JP4385962B2 - Control device for internal combustion engine - Google Patents

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal combustion engine control apparatus, and more particularly, to an internal combustion engine control suitable as an apparatus for controlling an internal combustion engine that includes a mechanism that varies an exhaust gas recirculation amount and a mechanism that varies an intake air amount. Relates to the device.

  Conventionally, for example, Japanese Patent Application Laid-Open No. 2002-22671 discloses a valve for an internal combustion engine so as to achieve both prevention of an increase in oil consumption (oil rise) during deceleration of the internal combustion engine and suppression of catalyst deterioration during deceleration. Techniques for optimizing timing and valve lift are disclosed.

  In an internal combustion engine, when the throttle opening is closed, that is, when deceleration is requested by the driver, fuel cut is generally executed to improve fuel consumption characteristics. For this reason, when the internal combustion engine is decelerated, the inside of the intake pipe is greatly reduced in negative pressure, and air that does not contain fuel flows from the intake passage to the exhaust passage.

  When a large negative pressure is generated in the intake pipe, the in-cylinder pressure of the internal combustion engine is easily reduced to a negative pressure. When the in-cylinder pressure is reduced to a negative pressure, oil consumption in the internal combustion engine increases due to so-called oil rise. For this reason, from the viewpoint of suppressing oil consumption, it is desirable that the intake pipe pressure during deceleration of the internal combustion engine is not excessively negative. As a countermeasure, a countermeasure for increasing the intake air amount at the time of deceleration as the number of revolutions is increased.

  On the other hand, the catalyst disposed in the exhaust passage of the internal combustion engine has a characteristic that it is easily deteriorated by receiving a lean gas supply in a high temperature environment. For this reason, in order to suppress the deterioration of the catalyst during the fuel cut, it is desired to reduce the amount of air flowing when the internal combustion engine is decelerated.

  The above-described conventional system attempts to suppress the amount of circulating air without optimizing the intake pipe pressure excessively when the internal combustion engine is decelerated by optimizing the valve timing and the valve lift amount. . For this reason, this system has an excellent characteristic in suppressing an increase in oil consumption accompanying the execution of the deceleration fuel cut and suppressing deterioration of the catalyst.

JP 2002-227671 A JP-A-10-299518 JP-A-10-115234 JP 2004-52677 A

  However, the above-described conventional system attempts to achieve both the contradiction of suppression of intake negative pressure and suppression of the flow rate of air by only adjusting the characteristics of the valve, that is, only adjusting the characteristics of a single actuator. is there. In this regard, the conventional system described above still leaves room for improvement in terms of both suppressing oil consumption and preventing catalyst deterioration.

  The present invention has been made to solve the above-described problems, and sufficiently suppresses both oil consumption and catalyst deterioration associated with the deceleration fuel cut without impairing stable operation characteristics of the internal combustion engine. An object of the present invention is to provide a control device for an internal combustion engine.

In order to achieve the above object, a first invention is a control device for an internal combustion engine,
Fuel cut means for performing fuel cut during deceleration of the internal combustion engine;
An EGR control mechanism for controlling the exhaust gas recirculation amount;
The fuel cut at high engine speed, so that the exhaust gas recirculation amount as compared with the fuel cut under low engine speed becomes a large amount, and controls the EGR control mechanism based on the engine speed EGR control means,
An intake air amount control mechanism for controlling the intake air amount;
The fuel cut at high engine speed, so that the intake air amount as compared with the fuel cut under low engine speed is reduced, the intake air amount control means that controls the intake air amount control mechanism When,
It is characterized by providing.

The second invention is the first invention, wherein
An actual EGR determination means for determining whether or not an actual value of the exhaust gas recirculation amount exceeds a determination value;
The intake air amount control means waits until the actual value of the exhaust gas recirculation amount exceeds a judgment value after fuel cut is started under a high engine speed, and controls to reduce the intake air amount Control delay means for starting the process.

The third invention is the second invention, wherein
The EGR variable mechanism includes a variable valve mechanism that varies a valve overlap period in which an intake valve opening period and an exhaust valve opening period overlap,
The EGR control means includes VVT control means for driving the variable valve mechanism to increase or decrease the internal exhaust gas recirculation amount,
The actual EGR determination means determines whether or not an actual value of the exhaust gas recirculation amount exceeds a determination value based on a state of the variable valve mechanism.

  According to a fourth aspect of the present invention, in the second or third aspect, the intake air amount control means determines the actual value of the exhaust gas recirculation amount after the fuel cut is started under a high engine speed. Until the value is exceeded, it is characterized by including means for maintaining the intake air amount equal to or higher than the start of fuel cut.

According to a fifth invention, in any one of the first to fourth inventions,
Actual EGR determination means for determining whether or not the actual value of the exhaust gas recirculation amount exceeds a determination value;
Fuel cut prohibiting means for prohibiting execution of fuel cut until the actual value of the exhaust gas recirculation amount exceeds a determination value after the fuel cut execution condition is satisfied;
It is characterized by providing.

  According to a sixth aspect of the present invention, in the fifth aspect of the present invention, the fuel cut prohibition canceling means for canceling the fuel cut prohibition when the fuel cut prohibition limit period elapses after the fuel cut execution condition is satisfied. It is characterized by providing.

According to a seventh invention, in any one of the first to sixth inventions,
With throttle opening electronic control means for electronically controlling the throttle opening based on the accelerator opening,
The fuel cut means determines whether or not a fuel cut execution condition is satisfied based on the accelerator opening.

Further, an eighth invention is any one of the first to seventh inventions,
EGR increase release means for releasing the increase correction of the exhaust gas recirculation amount by the EGR control means when the fuel cut duration reaches a predetermined time;
A reduction release means for releasing the reduction correction of the intake air amount by the intake air amount control means when the fuel cut duration time reaches the predetermined time;
It is characterized by providing.

  According to a ninth aspect, in the eighth aspect, after the start of the fuel cut, when the catalyst disposed in the exhaust passage of the internal combustion engine is presumed to have fully occluded oxygen, the duration time is the predetermined time. It further comprises a duration determination means for determining that the time has been reached.

The tenth invention is the ninth invention, wherein
The catalyst includes an upstream catalyst and a downstream catalyst arranged in series,
A downstream oxygen sensor disposed downstream of the upstream catalyst;
The duration determination means is
An air amount integrating means for calculating an integrated intake air amount from the time when the output of the downstream oxygen sensor becomes a lean output after the start of fuel cut;
And determining means for determining that the duration has reached the predetermined time when the accumulated intake air amount reaches a value that allows the downstream catalyst to fully store oxygen.

The eleventh aspect of the invention is the tenth aspect of the invention,
Upstream oxygen storage capacity detection means for detecting the oxygen storage capacity of the upstream catalyst;
A setting means for setting a value for fully storing oxygen in the downstream catalyst based on an oxygen storage capacity of the upstream catalyst;
Is further provided.

In addition, a twelfth aspect of the invention is any one of the eighth to eleventh aspects of the invention.
Cooling flow rate realization means for controlling the intake air amount to a cooling target flow rate that is larger than the flow rate before the start of the fuel cut when the fuel cut duration time reaches the predetermined time;
When the target cooling flow rate is maintained for a predetermined cooling time while the fuel cut is continued, the intake air amount is larger than the flow rate before the start of the fuel cut, and compared with the target cooling flow rate. And a flow rate changing means for controlling the flow rate to be small,
It is characterized by providing.

The thirteenth invention in the twelfth invention,
Catalyst temperature detection estimating means for detecting or estimating the temperature of the catalyst disposed in the exhaust passage of the internal combustion engine;
Cooling time setting means for setting the cooling time based on the temperature of the catalyst;
It is characterized by providing.

In addition, a fourteenth invention is according to any one of the first to thirteenth inventions,
It said EGR control means,
And operating speed detecting means for detecting the operating speed before Symbol EGR adjustment mechanism,
An operation amount setting means for setting the operation amount of the EGR variable mechanism at the time of fuel cut based on the operation speed;
It is characterized by including.

  In a fifteenth aspect based on the fourteenth aspect, the intake air amount control means sets the throttle amount of the intake air amount at the time of fuel cut to a smaller value as the operating amount increases. It is characterized by including.

  According to a sixteenth aspect, in the fourteenth or fifteenth aspect, the operating speed detecting means detects an operating speed of the EGR variable mechanism in a region where the engine speed exceeds a determination value. .

The seventeenth invention is the sixteenth invention, in which
The operating speed detecting means includes
An operating speed measuring means for measuring the operating speed of the EGR variable mechanism at an arbitrary engine speed;
A rotational speed storage means for storing the engine rotational speed at the time of measuring the operating speed;
Conversion means for converting the operating speed measured by the operating speed measuring means into an operating speed in a region exceeding the determination value based on the engine speed at the time of measurement;
It is characterized by providing.

The eighteenth aspect of the invention is any one of the fourteenth to seventeenth aspects of the invention,
The EGR variable mechanism uses the hydraulic pressure of the internal combustion engine as a drive source,
The operating speed detecting means includes
An operating speed measuring means for measuring the operating speed of the EGR variable mechanism at an arbitrary oil temperature;
Oil temperature storage means for storing the oil temperature at the time of measuring the operating speed;
Oil temperature detecting means for detecting the oil temperature at a predetermined timing;
Conversion means for converting the operating speed measured by the operating speed measuring means into the operating speed at the predetermined timing based on the oil temperature at the time of measurement and the oil temperature at the predetermined timing;
It is characterized by providing.

  In a nineteenth aspect based on the twelfth aspect, the cooling flow rate realizing means and the flow rate changing means control the intake air amount by controlling a throttle opening or an idle speed control (ISC) valve flow rate. It is characterized by that.

The twentieth aspect of the invention is any one of the first to nineteenth aspects of the invention.
The intake air amount variable mechanism includes a throttle valve or an idle speed control (ISC) valve,
The intake air amount control means controls the intake air amount by controlling a throttle opening or an idle speed control (ISC) valve flow rate.

According to the first invention, at the time of fuel cut under a high engine speed, a large amount of exhaust gas recirculation can be generated and the amount of intake air can be reduced. If a large amount of exhaust gas recirculation is ensured, excessive intake negative pressure can be avoided even if fuel cut is performed under high engine speed. Further, in this case, it is possible to avoid excessive leaning of the gas flowing into the catalyst even during the fuel cut. For this reason, according to the present invention, when fuel cut is executed at a high engine speed, deterioration of the catalyst can be sufficiently suppressed while sufficiently suppressing oil rise. Further, according to the present invention, the exhaust gas recirculation amount is suppressed and the intake air amount is reduced under a low engine speed at which the operating state of the internal combustion engine tends to become unstable, unlike under a high engine speed. The aperture is also suppressed. For this reason, according to the present invention, it is possible to prevent the operation of the internal combustion engine from becoming unstable when returning from the fuel cut under the low engine speed.

  According to the second invention, when the fuel cut is started under a high engine speed, after the command to increase the exhaust gas recirculation amount is actually reached, until the completion of the order exceeds the judgment value, You can wait to reduce the amount of intake air. If the intake air amount is reduced before the exhaust gas recirculation amount is actually ensured, the intake pipe pressure temporarily becomes excessively negative, and the oil rises easily. According to the present invention, it is possible to prevent such a situation from occurring and reliably prevent an increase in oil consumption.

  According to the third invention, the exhaust valve recirculation amount (internal EGR amount) can be increased or decreased by controlling the variable valve mechanism and changing the valve overlap period. In this case, the actual internal EGR amount is determined according to the state of the variable valve mechanism. According to the present invention, it is possible to accurately determine whether or not the exhaust gas recirculation amount exceeds the determination value based on the state of the variable valve mechanism.

  According to the fourth aspect of the invention, the intake air amount can be maintained in a large amount until the exhaust gas recirculation amount is sufficiently secured after the fuel cut is started at a high engine speed. Therefore, according to the present invention, it is possible to reliably prevent the intake pipe pressure from becoming excessively negative immediately after the start of the fuel cut.

  According to the fifth aspect, after the fuel cut execution condition is satisfied, the execution of the fuel cut can be prohibited until the actual value of the exhaust gas recirculation amount is sufficiently secured. For this reason, according to the present invention, it is possible to prevent a large amount of lean gas from flowing into the catalyst immediately after the start of the fuel cut, and to effectively prevent the deterioration of the catalyst from proceeding.

  According to the sixth aspect of the present invention, after the fuel cut execution condition is satisfied, after the fuel cut prohibition limit period has passed, the fuel cut execution is started even if the exhaust gas recirculation amount is not sufficiently secured. Can be made. For this reason, according to the present invention, it is possible to appropriately generate the feeling of deceleration expected by the driver.

  According to the seventh aspect, it is possible to determine the feasibility of the fuel cut execution condition based on the accelerator opening without using the throttle opening as a basis. Therefore, according to the present invention, it is possible to quickly determine whether the fuel cut condition is satisfied without being affected by the time difference until the accelerator opening is reflected in the throttle opening.

  According to the eighth aspect of the invention, when the fuel cut duration reaches a predetermined time, the exhaust gas recirculation amount increase correction can be canceled, and the intake air amount decrease correction can be canceled. If the fuel cut continues for a long period of time, the inside of the catalyst is saturated with oxygen, so the reason for suppressing the inflow of lean gas to the catalyst disappears. Rather, in this case, for stable operation after fuel cut, it is better to reduce the exhaust gas recirculation amount and increase the air amount to prevent the oil from rising. According to the present invention, in response to the above requirements, it is possible to enable stable operation of the internal combustion engine after fuel cut.

  According to the ninth aspect, the continuation of the predetermined time can be determined in synchronization with the time when the catalyst is saturated with oxygen. Therefore, according to the present invention, it is possible to create a situation advantageous for stable operation after fuel cut as early as possible while sufficiently protecting the catalyst.

  According to the tenth aspect of the invention, after a lean gas starts to blow downstream of the upstream catalyst disposed in the exhaust passage, the predetermined intake time continues when the accumulated intake air amount sufficient to saturate the downstream catalyst with oxygen flows. Can be determined. According to the above determination method, the post-difference of the oxygen storage amount of the upstream catalyst can be excluded from the determination elements, and therefore the determination accuracy regarding the continuation of the predetermined time can be sufficiently increased.

  According to the eleventh aspect, the value of the cumulative intake air amount necessary for saturating the downstream catalyst with oxygen can be set based on the oxygen storage capacity of the upstream catalyst. The amount of air required to saturate the downstream catalyst with oxygen is determined according to the oxygen storage capacity of the downstream catalyst. A high correlation is observed between the oxygen storage capacity of the downstream catalyst and the oxygen storage capacity of the upstream catalyst. For this reason, according to the present invention, it is possible to accurately set the value of the cumulative intake air amount for saturating the downstream catalyst with oxygen.

  According to the twelfth aspect, when the fuel cut duration reaches a predetermined time, that is, when it is determined that the necessity to suppress the inflow of air to the catalyst has disappeared, the intake air amount is reduced to the cooling target flow rate. It can be. In this case, since a large amount of intake air is allowed to flow, cooling of the catalyst is promoted. Even if the catalyst is exposed to lean gas, the catalyst will not deteriorate rapidly if its temperature is low. According to the present invention, in a situation where oxygen saturation of the catalyst is inevitable, the progress of deterioration can be suppressed by rapidly cooling the catalyst. Furthermore, according to the present invention, after the catalyst has been sufficiently cooled (after the cooling time has elapsed), it is possible to effectively prevent the occurrence of oil rising by appropriately securing the amount of intake air. .

  According to the thirteenth aspect, the cooling time can be set based on the temperature of the catalyst. For this reason, according to the present invention, the amount of intake air can be set to the cooling target flow rate for an appropriate period without excess or deficiency in cooling the catalyst.

  According to the fourteenth aspect, the operating amount of the EGR variable mechanism at the time of fuel cut can be set based on the operating speed of the EGR variable mechanism detected in advance. If the operating amount during fuel cut is set based on the operating speed of the EGR variable mechanism, the EGR variable mechanism can be returned to a state suitable for normal operation without significant delay when returning from the fuel cut. Can do. For this reason, according to the present invention, it is possible to always prevent the state of the internal combustion engine from becoming unstable when returning from the fuel cut.

  According to the fifteenth aspect, the throttle amount of the intake air amount at the time of fuel cut can be set to a smaller value as the operating amount of the EGR variable mechanism is larger. That is, according to the present invention, in a situation where the operation amount of the EGR variable mechanism is large and the EGR amount is sufficiently secured, the intake air amount is sufficiently reduced, while the operation amount of the EGR variable mechanism is small, In a situation where the amount is not sufficiently secured, the intake air amount can be increased to some extent. For this reason, according to the present invention, it is possible to always create an optimum situation in order to achieve both oil increase and catalyst protection, on the premise of the set operation amount during the fuel cut.

  According to the sixteenth aspect, the operating speed indicated by the EGR variable mechanism can be detected in a region where the engine speed exceeds the determination value. The EGR variable mechanism is required to have a larger operation amount as the engine speed is higher. Therefore, in order to guarantee that the EGR variable mechanism can return to the state suitable for the receiving operation without delay when returning from the fuel cut, the operation amount of the EGR variable mechanism is set based on the operation speed in the high rotation range. It is appropriate to keep it. According to the present invention, since the requirement can be satisfied, the stability of the internal combustion engine at the time of return from the fuel cut can be reliably ensured.

  According to the seventeenth aspect, the operating speed in the region exceeding the determination value can be detected by converting the operating speed of the EGR variable mechanism measured at an arbitrary engine speed. According to such a method, it is possible to acquire the operating speed of the EGR variable mechanism without waiting for the internal combustion engine to enter the high rotation range. For this reason, according to the present invention, the operating speed of the EGR variable mechanism can be quickly acquired after the internal combustion engine is started.

  According to the eighteenth aspect, the operating speed at a predetermined timing can be detected by converting the operating speed of the EGR variable mechanism measured at any oil temperature. Since the EGR variable mechanism uses hydraulic pressure as a drive source, the operation speed varies depending on the oil temperature. According to the present invention, it is possible to detect an appropriate operating speed at a predetermined timing without being affected by fluctuations in the oil temperature. For this reason, according to this invention, the stable driving | running state is always realizable at the time of the return from a fuel cut.

  According to the nineteenth or twentieth invention, the required change in the intake air amount can be easily and accurately realized by controlling the throttle opening or the idle speed control (ISC) valve flow rate.

Embodiment 1 FIG.
[Description of system configuration]
FIG. 1 is a diagram for explaining the configuration of the first embodiment of the present invention. As shown in FIG. 1, the system of the present embodiment includes an internal combustion engine 10. An intake passage 12 and an exhaust passage 14 communicate with the internal combustion engine 10.

  An air flow meter 16 that detects the amount of air flowing through the intake passage 12, that is, the amount of intake air Ga flowing into the internal combustion engine 10, is arranged. A throttle valve 18 is disposed downstream of the air flow meter 16. The throttle valve 18 is an electronically controlled valve that is driven by the throttle motor 20 based on the accelerator opening. A throttle position sensor 22 for detecting the throttle opening degree TA and an accelerator position sensor 24 for detecting the accelerator opening degree AA are arranged in the vicinity of the throttle valve 18.

  The internal combustion engine 10 is a multi-cylinder engine having a plurality of cylinders, and FIG. 1 shows a cross section of one of the cylinders. Each cylinder included in the internal combustion engine 10 is provided with an intake port that communicates with the intake passage 12 and an exhaust port that communicates with the exhaust passage 14. A fuel injection valve 26 for injecting fuel into the intake port is disposed in the intake port. The intake port and the exhaust port are provided with an intake valve 28 and an exhaust valve 30, respectively, for bringing the intake passage 12 and the cylinder or the exhaust passage 14 and the cylinder into a conductive state or a cutoff state.

  The intake valve 28 and the exhaust valve 30 are driven by variable valve (VVT) mechanisms 32 and 34, respectively. The variable valve mechanisms 32 and 34 open and close the intake valve 28 and the exhaust valve 30 in synchronization with the rotation of the crankshaft, and change their valve opening characteristics (valve opening timing, operating angle, lift amount, etc.). can do.

  The internal combustion engine 10 includes a crank angle sensor 36 in the vicinity of the crankshaft. The crank angle sensor 36 is a sensor that reverses the Hi output and the Lo output each time the crankshaft rotates by a predetermined rotation angle. According to the output of the crank angle sensor 36, it is possible to detect the rotational position and rotational speed of the crankshaft, and further the engine rotational speed NE and the like.

  In the exhaust passage 14 of the internal combustion engine 10, an upstream catalyst (SC) 38 and a downstream catalyst (UF) 40 for purifying exhaust gas are arranged in series. Further, an air-fuel ratio sensor 42 for detecting the exhaust air-fuel ratio at that position is disposed upstream of the upstream catalyst 38. Further, an oxygen sensor 44 that generates a signal corresponding to whether the air-fuel ratio at that position is rich or lean is disposed between the upstream catalyst 38 and the downstream catalyst 40.

  The system shown in FIG. 1 includes an ECU (Electronic Control Unit) 50. The ECU 50 is connected to the various sensors and actuators described above. The ECU 50 can control the operating state of the internal combustion engine 10 based on those sensor outputs.

[Features of Embodiment 1]
(F / C operation under high NE)
The system according to the present embodiment executes a process of stopping fuel injection, that is, fuel cut (F / C) when the throttle opening degree TA is set to an idle opening degree during the operation of the internal combustion engine 10. FIG. 2 is a timing chart for explaining the operation of this embodiment when F / C is executed in an environment where the engine speed NE is sufficiently high.

  More specifically, FIG. 2 (A) shows a waveform representing the execution state of F / C. Here, a case where F / C is started at time t0 is illustrated. FIG. 2B shows a waveform of the intake pipe pressure PM. However, the broken line in FIG. 2 (B) is the allowable limit value of the intake pipe pressure PM that does not cause oil rise or oil fall. FIG. 2C shows a waveform representing a change in internal EGR (Exhaust Gas Recirculation). FIG. 2D shows a waveform representing a change in the throttle opening degree TA. Specifically, an example is shown in which the throttle opening degree TA is suddenly closed immediately before time t0.

  F / C is started when the throttle opening TA is suddenly closed during the operation of the internal combustion engine 10. For this reason, after the start of F / C, a state is formed in which the intake pipe pressure PM is large and easily becomes negative. At this time, if the intake pipe pressure PM exceeds the allowable limit value and becomes negative, oil rises (ingress of oil from the periphery of the piston into the combustion chamber) and oil falls (oil from the periphery of the valve stem to the combustion chamber). ) Occurs and the oil consumption increases.

  Incidentally, the negative pressure of the intake pipe pressure PM can be avoided by increasing the throttle opening degree TA. Accordingly, after the start of F / C, the throttle opening TA is larger than the basic idle opening TA0 (the idle opening in the low rotation region), particularly in the high rotation region where the intake pipe pressure PM is likely to become large and negative. If the opening is maintained, the intake pipe pressure PM can be maintained at a pressure higher than the allowable limit value to prevent the oil from rising or falling.

  However, since fuel injection is not performed during execution of F / C, the gas flowing into the catalyst (upstream catalyst 38 and downstream catalyst 40) is extremely lean. When a lean gas flows into the high-temperature catalyst, the catalyst tends to deteriorate. For this reason, if the throttle opening TA is opened after the start of F / C to increase the amount of lean gas flow, the increase in oil consumption can be prevented, but the deterioration of the upstream catalyst 38 and the downstream catalyst 40 is promoted.

  According to the system shown in FIG. 1, the valve opening period of the exhaust valve 30 is retarded by the variable valve mechanism 34, so that both the intake valve 28 and the exhaust valve 30 are opened. The period can be extended. If the valve overlap period is extended, the amount of burned gas that flows back to the intake passage 14 after the intake valve 28 is opened, that is, the internal EGR amount increases.

  The intake pipe pressure PM approaches the atmospheric pressure as the amount of gas downstream of the throttle valve 18 increases. The amount of gas is the sum of the amount of fresh gas that has passed through the throttle valve 18 and the amount of internal EGR gas generated during the valve overlap period. For this reason, if the internal EGR amount is sufficiently large, the intake pipe pressure PM will not be excessively negative, no matter how small the throttle opening TA is.

  Furthermore, if the throttle opening degree TA is reduced with the internal EGR amount sufficiently secured, the burned gas ratio in the cylinder can be sufficiently increased. If such a state is realized during the execution of F / C, it is possible to avoid an extreme leaning of the gas flowing into the catalyst.

  As described above, according to the system shown in FIG. 1, even when F / C is started in the high speed region, the throttle opening TA is generated in a state where a valve overlap is generated so that sufficient internal EGR is generated. If this is sufficiently reduced, it is possible to effectively suppress the deterioration of the upstream catalyst 38 and the downstream catalyst 40 while preventing the oil from rising or falling.

  However, in the configuration shown in FIG. 1, after a command is issued to the variable valve mechanism 34, until a desired internal EGR amount is actually obtained, that is, a desired valve overlap is actually obtained. Until that time, the operation time of the actuator is required. For this reason, as shown in FIG. 2C, the actual value of the internal EGR amount reaches the convergence value after the above operation time after the start of F / C (after time t0).

  If the throttle opening degree TA is throttled before the internal EGR amount sufficiently approaches the convergence value, the problem of oil increase or oil decrease inevitably occurs. Therefore, in the present embodiment, as shown in FIG. 2D, after the start of F / C, the throttle opening TA is temporarily set to the basic idle until the actual value of the internal EGR amount reaches a sufficient amount. A value larger than the opening degree TA0 is set, and thereafter, when the internal EGR amount is sufficiently secured, the throttle opening degree TA is subjected to aperture correction. According to such a throttle operation, after the start of F / C, it is possible to prevent the intake pipe pressure PM from becoming excessively negative while keeping the air flow rate sufficiently small. For this reason, according to the apparatus of this embodiment, it is possible to effectively prevent an increase in oil consumption and catalyst deterioration due to execution of F / C.

(F / C operation under low NE)
The above-described operation is an operation when F / C is started under a high NE. If the engine speed NE is sufficiently high, burned gas is present in the cylinder at a high rate during F / C execution, and even if a large valve overlap is ensured, before the end of F / C By reducing the overlap, the normal stable operation state can be restored before the engine stall occurs.

  However, if the same condition as above is formed during F / C in the region where the engine speed NE is low, after the completion of F / C, before the fresh air ratio of the in-cylinder gas becomes sufficiently high, The internal combustion engine 10 may reach a stalled state. For this reason, when the F / C is executed under a low NE, the system of the present embodiment shortens the valve overlap period as compared to during the F / C under a high NE, and The throttle opening TA is to be loosened.

  According to such processing, it is possible to immediately reproduce a situation where stable operation is possible immediately after the F / C executed under the low NE is terminated. For this reason, according to the system of the present embodiment, it is possible to effectively prevent the internal combustion engine 10 from stalling after completion of the F / C under the low NE.

[Specific Processing in Embodiment 1]
FIG. 3 is a flowchart of a routine executed by the ECU 50 in the present embodiment in order to realize the above function. According to the routine shown in FIG. 3, first, the engine speed NE and the load factor kl are taken in (step 100). The engine speed NE can be acquired based on the output of the crank angle sensor 36. The load factor kl is a ratio between the intake air amount obtained when the throttle opening degree TA is fully opened and the actual intake air amount Ga, and can be acquired based on the output of the air flow meter 16 or the like.

  Next, the normal target value vt1 of the variable valve mechanism 34 is calculated based on the engine speed NE and the load factor kl (step 102). The normal target value vt1 is a target value of the valve timing VVT during normal operation that is not in F / C. As shown in FIG. 4, the ECU 50 stores a map in which the normal target value vt1 is determined by the relationship between the engine speed NE and the load factor kl. Here, the normal target value vt1 is calculated by referring to the map.

  According to the map shown in FIG. 4, for example, in the low load region where the load factor kl is 10% or less, the normal target value vt1 is set to 0 whatever the engine speed NE is. When the normal target value vt1 = 0 is realized, the valve overlap does not occur. Therefore, as long as the normal target value vt1 is used, no internal EGR gas is generated in the low load region.

  In the routine shown in FIG. 3, it is next determined whether or not the deceleration F / C condition is satisfied (step 104). More specifically, it is determined here whether the throttle opening degree TA is closed to the basic idle opening degree TA0.

  When the throttle opening TA is larger than the basic idle opening TA0, the deceleration F / C condition is not satisfied. In this case, in order to continue the normal operation, first, the valve timing VVT is controlled toward the normal target value vt1 (step 106).

  Next, the throttle opening degree TA is controlled in accordance with the accelerator opening degree AA (step 108). Thereafter, 0 is set to the F / C execution flag XFC to indicate that execution of F / C is prohibited (step 110). When the above processing is executed, the internal combustion engine 10 continues normal operation according to the accelerator operation amount of the driver. l

  In the routine shown in FIG. 3, when the establishment of the deceleration F / C condition is established at step 104 (TA ≦ TA0), the deceleration target value vt2 of the valve timing VVT is calculated (step 112). ). The deceleration target value vt2 is a value of the valve timing VVT to be realized during the execution of the deceleration F / C.

  FIG. 5 shows an example of a map stored in the ECU 50 for calculating the deceleration target value vt2. In the map shown in FIG. 5, the deceleration target value vt2 is determined in relation to the engine speed NE. More specifically, the deceleration target value vt2 is set to 0 near the idle speed, and is set to a larger value (maximum value 20) as the engine speed NE becomes higher.

  The deceleration target value vt2 is a target value used in a situation where the load factor kl is sufficiently smaller than 10%. The normal target value vt1 is set to 0 in the entire rotation region under such a situation. Therefore, the deceleration target value vt2 is set to become larger as the engine speed NE becomes higher than the normal target value vt1.

  The system of this embodiment is configured such that the valve overlap period becomes longer as the valve timing VVT becomes larger. As described above, the internal EGR amount increases as the valve overlap period increases. For this reason, when the valve timing VVT is set to the deceleration target value vt2, the higher the engine speed NE, the longer the valve overlap period is secured, and as the engine speed NE becomes lower, The valve overlap period is reduced toward zero.

  In the routine shown in FIG. 3, it is next determined whether or not the actual valve timing vtt exceeds the determination value α ° CA (step 114). In the system of the present embodiment, after a command for making the valve timing VVT coincide with the deceleration target value vt2 is issued to the variable valve mechanism 34, until the VVT actually matches vt2, to some extent. Actuator operating time is required. That is, in the system of the present embodiment, after the deceleration target value vt2 is determined, a certain amount of time is required until an internal EGR amount sufficient to avoid the occurrence of excessive intake negative pressure is secured. . The condition of vtt> α ° CA used in step 112 is substantially a condition for determining whether the actual valve timing vtt has changed to such an extent that a desired internal EGR amount is ensured.

  FIG. 6 is an example of a map stored in the ECU 50 for setting the determination value α. That is, the ECU 50 sets the determination value α with reference to the map shown in FIG. According to the map shown in FIG. 6, the determination value α is maintained at the minimum value in the low NE region, increases or decreases in proportion to the NE in the middle NE region, and is maintained at the maximum value in the high NE region. . In the low NE region, it is possible to avoid the occurrence of excessive intake negative pressure without requiring a large valve overlap. On the other hand, in the high NE region, a large valve overlap is necessary to prevent excessive intake negative pressure. According to the map shown in FIG. 6, it is possible to set a determination value α with no excess or deficiency in all the NE regions according to the difference in the circumstances.

  In the routine shown in FIG. 3, if it is determined in step 114 that vtt> α ° CA is not established, it can be determined that a sufficient internal EGR amount has not yet been secured. In this case, next, a process for setting the first target throttle opening degree ta1 at the time of deceleration F / C is executed. More specifically, here, first, the first correction value kfcta1 is calculated (step 116).

In the present embodiment, the ECU 50 calculates a target value (target ta) of the throttle opening TA by the following equation.
Target ta = Basic idle opening TA0 + first correction coefficient kfcta1−second correction coefficient kfcta2
... (1)

  According to the above equation (1), the target ta becomes a larger value as the first correction coefficient kfcta1 is larger, while it becomes a smaller value as the second correction coefficient kfcta2 is larger. That is, the first correction coefficient kfcta1 is a correction coefficient for expanding the target ta, and the second correction coefficient kfcta2 is a correction coefficient for narrowing the target ta.

  FIG. 7 shows an example of a map stored in the ECU 50 for calculating the first correction coefficient kfcta1. In step 116, the first correction coefficient kfcta1 is calculated by referring to this map. According to this map, the first correction coefficient kfcta1 is set to a larger value as the engine speed NE is higher, and is set to a minimum value 0 when the engine speed NE is a value close to the idle speed. The

  When the calculation of the first correction coefficient kfcta1 is completed, next, the second correction coefficient kfcta2 is set to 0 (step 118). According to the above processing, the target ta is set to a larger value as compared with the basic idle opening degree TA0 as the engine speed NE is higher. Here, the target ta having such characteristics is referred to as a first target throttle opening degree ta1.

  In the routine shown in FIG. 3, if the establishment of vtt> α ° CA is confirmed in step 114, it is determined that the internal EGR amount sufficient to avoid the occurrence of excessive intake negative pressure is already secured. be able to. In this case, thereafter, processing for calculating the second target throttle opening degree ta2 at the time of deceleration F / C is executed.

  Here, first, the first correction coefficient kfcta1 is set to 0 (step 120). Next, the second correction coefficient kfcta2 is calculated with reference to the map shown in FIG. 8 (step 122).

  In the map shown in FIG. 8, the second correction coefficient kfcta2 becomes larger as the engine speed NE is higher, and the second correction coefficient kfcta2 is the minimum value 0 when the engine speed NE is close to the idle speed. It is determined to be. Since the second correction coefficient kfcta2 is a correction coefficient for narrowing down the target ta, according to the processing in steps 120 and 122, the target ta is higher than the basic idle opening degree TA0 as the engine speed NE is higher. It will be set to a small value. Here, the target ta having such characteristics is referred to as a second target throttle opening degree ta2.

  According to the routine shown in FIG. 3, it is next determined whether or not the engine speed NE is higher than the F / C start speed A (step 124). As a result, when NE> A is established, 1 is set to the F / C execution flag XFC (step 126).

  The ECU 50 monitors the state of the F / C execution flag XFC by another routine, and executes F / C when it is recognized that XFC = 1 is established. For this reason, when the process of step 126 is executed, F / C is started in the internal combustion engine 10 thereafter.

  In the routine shown in FIG. 3, next, control for setting the valve timing VVT to the deceleration target value vt2 is executed (step 128). As a result, in the region where the engine speed NE is high, the valve timing VVT is corrected so as to ensure a large valve overlap, and the internal EGR amount is increased.

  Next, the throttle valve 18 is controlled so that the throttle opening degree TA coincides with the target ta obtained by the above equation (1) (step 130). As described above, the target ta is set to a value equal to or higher than the first target throttle opening degree ta1, that is, the basic idle opening degree TA0 until the actual valve timing vtt reaches α ° CA. In this case, the higher the engine speed NE, the larger the throttle opening TA. As a result, even before a sufficient internal EGR amount is generated, excessive intake negative pressure is avoided, and an increase in oil consumption is prevented.

  The target ta is also set to a value equal to or less than the second target throttle opening degree ta2, that is, the basic idle opening degree TA0, after the actual valve timing vtt reaches α ° CA. In this case, the higher the engine speed NE, the smaller the throttle opening TA, and the smaller the flow rate of fresh gas flowing into the upstream catalyst 38 and the downstream catalyst 40. As a result, deterioration of the upstream catalyst 38 and the downstream catalyst 40 during execution of F / C is suppressed.

  In the routine shown in FIG. 3, if it is determined in step 124 that NE> A is not satisfied, it is next determined whether or not the F / C execution flag XFC is set to 1 (step 132). . If the establishment of XFC = 1 is recognized, it can be determined that the F / C has already started. In this case, it is next determined whether or not the engine speed NE has decreased to the F / C end speed B (step 134).

  If it is determined that the engine rotational speed NE is greater than the F / C end rotational speed B, it can be determined that the F / C end condition is still not satisfied. In this case, the processes of steps 128 and 130 are executed again in that order.

  On the other hand, if it is determined in step 132 that XFC = 1 is not established, it can be determined that the situation for starting F / C is not established. Further, when NE> B is not established in step 134, it can be determined that the condition for ending F / C is established. In these cases, the processes in steps 106 to 110 are sequentially executed in order to realize the normal operation state.

  As described above, according to the routine shown in FIG. 3, in the region where the engine speed NE is high, the throttle opening TA is increased after the start of F / C until the internal EGR amount is secured. Thus, an increase in oil consumption can be prevented. Also, during F / C in this region, by reducing the throttle opening TA when the internal EGR amount is sufficiently secured, both increase in oil consumption and prevention of catalyst deterioration must be achieved. Can do.

  Further, according to the routine shown in FIG. 3, both the valve timing VVT and the throttle opening degree TA are set to the normal operation state in the region where the engine speed NE is low even during the execution of F / C. You can get closer. For this reason, according to the system of the present embodiment, it is possible to reliably prevent the operating state of the internal combustion engine 10 from becoming unstable after the F / C is finished in the low rotation region.

  In the first embodiment described above, the valve overlap period is changed by changing the state of the variable valve mechanism 34 that drives the exhaust valve 30, and as a result, the internal EGR amount is changed. The method for changing the internal EGR amount is not limited to such a method. For example, the valve overlap period may be changed by changing the state of the variable valve mechanism 32 that drives the intake valve 28, and as a result, the internal EGR amount may be changed.

  Further, the method of changing the internal EGR amount is not limited to the method of increasing or decreasing the valve overlap period. For example, when the valve closing timing of the exhaust valve 30 is set in the crank angle region before the exhaust top dead center, the amount of residual gas trapped in the cylinder in the exhaust stroke increases or decreases by moving the valve closing timing back and forth. For this reason, the internal EGR amount may be increased or decreased by adjusting the closing timing of the exhaust valve 30 in the crank angle region before the exhaust top dead center.

  Further, in the first embodiment described above, it is possible to prevent excessive negative pressure and excessive lean in the intake passage 12 by increasing the internal EGR amount during F / C under high NE. However, the prevention method is not limited to this. That is, a similar function may be realized by providing an EGR mechanism for recirculating exhaust gas discharged to the exhaust passage 14 to the intake passage 12 and increasing the external EGR amount.

  In the first embodiment described above, the throttle opening TA waits for the actual valve timing vtt to exceed the determination value α ° CA, that is, waits for the actual value of the internal EGR amount to be secured to some extent. However, the present invention is not limited to this. In other words, the reduction correction of the throttle opening TA after the start of F / C is such that the reduction amount of TA corresponds to the increase amount of the EGR amount as the actual value of the internal (or external) EGR amount increases. It is good also as performing to.

  In the first embodiment described above, the magnitude of the negative pressure and the flow rate of the air flowing through the catalyst are controlled by controlling the throttle opening, but the control target is limited to this. It is not a thing. That is, the magnitude of the negative pressure and the flow rate of the air flowing through the catalyst can be controlled by increasing or decreasing the intake air amount Ga. Therefore, the same function as that of the first embodiment can be achieved not only by controlling the throttle opening but also by controlling an element that changes the intake air amount. Specifically, in the case of a throttleless internal combustion engine, an internal combustion engine provided with an idle speed control (ISC) valve that bypasses the throttle valve by changing the lift amount, operating angle, valve opening timing, etc. of the intake valve. In the case of an engine, the same function as in the first embodiment can be realized by changing the flow rate of the ISC valve passing therethrough.

  In the first embodiment described above, the ECU 50 executes F / C when the internal combustion engine 10 is decelerated, so that the “fuel cut means” in the first invention executes the processing of steps 112 and 128. As a result, the “EGR control means” in the first invention and the “VVT control means” in the third invention execute the processing of steps 122 and 130 to thereby execute the “intake air amount control means” in the first invention. "Is realized.

  Further, in the first embodiment described above, the ECU 50 executes the process of step 114, so that the “real EGR determination means” in the second or third invention waits for the condition of step 114 to be satisfied. The “control delay means” according to the second aspect of the present invention is implemented by executing the processes of steps 122 and 122.

  Further, in the first embodiment described above, the “means for maintaining the intake air amount” in the fourth aspect of the present invention is realized by the ECU 50 executing the processing of steps 116 and 118.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIG. 9 and FIG. The system of the present embodiment can be realized by causing the ECU 50 to execute a routine shown in FIG. 10 to be described later, using the hardware configuration shown in FIG.

[Features of Embodiment 2]
FIG. 9 is a timing chart for explaining characteristic operations of the system according to the second embodiment of the present invention. More specifically, FIG. 9A shows a waveform representing success / failure of the F / C condition. Further, FIG. 9B is a chart that virtually represents a change example (two examples) of the actual valve timing vtt before and after the establishment of the F / C condition. Further, FIG. 9C is a chart virtually showing a change example (two examples) of the throttle opening TA corresponding to a change example of the actual valve timing vtt shown in FIG. 9B. FIG. 9D is a chart showing F / C execution rules used in this embodiment.

  FIG. 9A shows an example in which the F / C execution condition is satisfied at time t0. As in the system of the first embodiment, when the F / C execution condition is satisfied, the system of the present embodiment subsequently changes the actual valve timing vtt so that the valve overlap increases in order to increase the internal EGR amount. Let

  The waveform indicated by the broken line in FIG. 9B shows an example in which the actual valve timing vtt has reached the determination value α ° CA in a relatively short time after time t0. Further, the waveform indicated by the alternate long and short dash line in FIG. 9B illustrates the case where a relatively long time is required until the actual valve timing vtt reaches the determination value α ° CA.

  As in the system of the first embodiment, the system according to the present embodiment sets the throttle opening TA to the basic idle time so as to avoid the occurrence of excessive intake negative pressure until the actual valve timing vtt reaches the determination value α ° CA. When the opening degree TA0 is maintained and vtt reaches α ° CA, the throttle opening degree TA is reduced to the basic idle opening degree TA0 or less. For this reason, the timing at which the throttle opening degree TA is throttled varies depending on the time until the actual valve timing vtt reaches the determination value α ° CA (see FIG. 9C).

  By the way, in the case where the above-described control rules are followed, a relatively large amount of fresh air flows through the internal combustion engine 10 until the throttle opening degree TA is reduced to the basic idle opening degree TA0 or less after F / C is started. Will be distributed. During this time, if F / C is actually executed according to the establishment of the F / C condition, a large amount of lean gas flows into the upstream catalyst 38 and the downstream catalyst 40, and their deterioration is promoted. In other words, in order to suppress the deterioration of the upstream catalyst 38 and the downstream catalyst 40, it is desirable not to actually start the F / C until the throttle opening degree TA is reduced regardless of the establishment of the F / C condition. .

  On the other hand, the driver of the vehicle expects that the braking force by the engine brake is generated when the accelerator pedal is released. In order to secure a large braking force, it is desirable that the F / C is actually started after the actual condition of the F / C is satisfied.

  Therefore, in this embodiment, the F / C execution rule is determined as shown in FIG. 9D to deal with the above-described two requests. That is, according to the execution rule shown in FIG. 9D, after the execution condition of F / C is satisfied, the period until time C is the F / C execution prohibition period. Here, the time C is the time after the F / C prohibition time C has elapsed after the time t0. The F / C prohibition time C is a time that is surely required for the actual valve timing vtt to reach the determination value α ° CA.

  Further, according to the rules shown in FIG. 9D, execution of F / C is permitted from time C to time D on condition that the actual valve timing vtt reaches the determination value α ° CA. Period. After time D, the execution of F / C is permitted regardless of the relationship between vtt and α. Here, the time D is a time after the prohibition limit time D has elapsed from the time t0. Further, the prohibition limit time D is the maximum time that can delay the start of execution of F / C in order to generate the braking force expected by the driver without a sense of incongruity.

  According to the F / C execution rules described above, until the actual valve timing vtt reaches the judgment value α ° CA, that is, as long as the F / C execution start can be delayed without a sense of incongruity, that is, the throttle opening TA is the basic idle. The execution of F / C can be delayed until the opening is reduced to an opening of TA0 or less. And if the predetermined time D has passed before vtt reaches α ° CA, the execution of F / C is permitted at that time, and the braking force expected by the driver is surely generated. Can do. For this reason, according to the system of this embodiment, it is possible to achieve both reliable protection of the upstream catalyst 38 and the downstream catalyst 40 and securing of the braking force expected by the driver.

[Specific Processing in Second Embodiment]
FIG. 10 is a flowchart of a routine executed by the ECU 50 in order to realize the above function. 10, the same steps as those shown in FIG. 3 are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  According to the routine shown in FIG. 10, while the deceleration F / C condition is not satisfied (while the throttle opening degree TA is larger than the basic idle opening degree TA0), steps 100 to 110 are performed as in the routine shown in FIG. The process is executed. As a result, a normal operation state is realized.

  When the throttle opening degree TA is closed to the basic idle opening degree TA0, the establishment of the deceleration F / C condition is recognized in step 104. In this case, the deceleration target value vt2 is calculated, and further, a process for setting the actual valve timing vtt to vt2 is executed (step 140). Note that the processing in step 140 is substantially a combination of the processing in step 102 and the processing in step 128 shown in FIG. 3, and therefore detailed description thereof is omitted here.

  Next, in the routine shown in FIG. 10, it is determined whether the F / C prohibit time C has elapsed after the deceleration F / C condition is satisfied (step 142). Immediately after the deceleration F / C condition is satisfied, it is determined that the F / C prohibit time C has not elapsed. In this case, after the second correction coefficient kfcta2 is set to 0 in step 118, the calculation of the first correction coefficient kfcta1 and the control of the throttle opening degree TA are executed (step 144).

  In step 144 described above, the first correction coefficient kfcta1 is calculated by the same method as in step 116 shown in FIG. 3, that is, by the method referring to the map shown in FIG. Further, the control of the throttle opening degree TA is executed with the target ta calculated by the above equation (1) as the target value, similarly to the case of step 130 shown in FIG. Here, since the first target throttle opening degree ta1 is calculated by the above equation (1), the throttle opening degree TA is controlled to an opening degree equal to or larger than the reference idle opening degree TA0.

  In the routine shown in FIG. 10, it is next determined whether or not the prohibition limit time D has not elapsed after the deceleration F / C condition is satisfied (step 146). When the F / C prohibition time C has not yet elapsed, the prohibition limit time D has not necessarily elapsed. For this reason, while the F / C prohibition time C has not yet elapsed, the condition of this step 146 is always satisfied, and thereafter the processing of step 110 is executed. As a result, after the deceleration F / C condition is satisfied, execution of F / C is always prohibited until at least the F / C prohibit time C elapses.

  If the throttle fully closed state continues for the F / C prohibited time C after the deceleration F / C condition is satisfied, in step 142, the passage of the F / C prohibited time C is determined. In this case, next, at step 114, it is judged if the actual valve timing vtt has reached the judgment value α ° CA.

  At this stage, if vtt has not yet reached α ° CA, it is determined that the condition of step 114 is not satisfied, and thereafter, the processing of steps 118, 144 and 146 is executed. As a result, until the prohibition limit time D elapses, execution of F / C is prohibited and the throttle opening TA is the first target unless the actual valve timing vtt reaches the judgment value α ° CA. The throttle opening degree ta1 is controlled.

  If the prohibition limit time D has elapsed before the actual valve timing vtt reaches the determination value α ° CA, it is determined in step 146 that the prohibition limit time D has elapsed. In this case, the process of step 124 is performed next.

  If the engine speed NE is equal to or lower than the F / C start speed A when the process of step 124 is executed for the first time after the deceleration F / C condition is satisfied, the condition of step 124 is not satisfied, and further Also, the condition of step 132 is not satisfied. In this case, the processing of steps 106 to 110 is subsequently performed, and the normal operation state is continued without starting the F / C.

  On the other hand, if NE> A is satisfied when the process of step 124 is executed for the first time after the deceleration F / C condition is satisfied, 1 is set to the F / C execution flag XFC in step 126, and F / C Is started. Thereafter, as long as the condition of step 104 is not satisfied, the processing of steps 124, 132 and 134 is repeated each time this routine is started, and the engine speed NE is decreased until the engine speed NE decreases to the F / C end speed B. Execution of / C continues.

  According to the above processing, even if it takes a long time for the actual valve timing vtt to reach α ° CA, after the deceleration limit time D has elapsed after the deceleration F / C condition is satisfied, the F / C Can start running. For this reason, according to the system of the present embodiment, in a situation where the driver expects to generate braking force by opening the accelerator, the braking force corresponding to the expectation is generated without giving the driver a sense of incongruity. Can be made.

  While the execution is continued after the start of F / C, it is determined whether the actual valve timing vtt exceeds the second determination value β ° CA following the processing of step 126 or 134 (step 148). . The second determination value β ° CA is larger than the determination value α ° CA and smaller than the deceleration target value vt2. For this reason, vtt> β is inevitably not established under a situation where Ftt is executed because vtt has not reached α ° CA and the prohibition limit time D has elapsed.

  In this case, the throttle opening degree TA is controlled in step 130 without performing the processing in step 122. Under the situation where vtt has not reached α ° CA, the target ta is set to the first target throttle opening degree ta1 by the processing of step 118 and step 144. Therefore, until vtt reaches α ° CA, the throttle opening degree TA is maintained at an opening degree equal to or higher than the basic idle opening degree TA0 even after the start of F / C.

  After the F / C prohibition time C has passed and the actual valve timing vtt has reached the judgment value α ° CA, the first correction is made in step 120 regardless of whether or not the prohibition limit time D has passed. The coefficient kfcta1 is set to zero. The first correction coefficient kfcta1 is a correction coefficient for widening the throttle opening degree TA. For this reason, when kfcta1 is set to 0, the throttle opening degree TA is subsequently suppressed to the basic idle opening degree TA0 or less.

  According to the above processing, after the actual valve timing vtt reaches the determination value α ° CA, that is, after a state in which the internal EGR amount can be secured to some extent is formed, a state in which a large amount of fresh air tends to flow in is not possible. It is possible to create an advantageous situation for preventing deterioration of the upstream catalyst 38 and the downstream catalyst 40 from being maintained as necessary.

  If NE> A or XFC = 1 is satisfied under the condition where vtt> α ° CA is satisfied, F / C is executed with the first correction coefficient kfcta1 being 0. While the F / C is being executed, every time the routine shown in FIG. 10 is started, it is determined in step 148 whether vtt> β ° CA is successful.

  As a result, after the actual valve timing vtt exceeds the determination value α ° CA, the process of step 122 is jumped until it reaches the second determination value β ° CA. In this case, in step 130, the target ta is calculated in a state where both the first correction coefficient kfcta1 and the second correction coefficient kfcta2 are zero. Therefore, the throttle opening degree TA is controlled to the basic idle opening degree TA0.

  According to the above processing, after the actual valve timing vtt exceeds the determination value α ° CA, when the deceleration is not sufficiently close to the deceleration target value vt2, that is, the internal EGR amount can be secured to some extent. Appropriate throttle opening TA that does not cause an unnecessarily large amount of fresh air to circulate and that does not excessively reduce the intake pipe pressure PM can be realized in cases where it cannot be sufficiently secured. .

  If the actual valve timing vtt reaches the second determination value β ° CA while the deceleration F / C condition is maintained, the condition at step 148 is satisfied. In this case, after the second correction coefficient kfcta2 is calculated in step 122 (the calculation method is the same as in step 122 in FIG. 3), the process of step 130 is executed.

  When the process of step 130 is performed subsequent to step 122, the throttle opening degree TA is controlled to the second target throttle opening degree ta2. For this reason, after vtt reaches β ° CA, the throttle opening degree TA can be reduced to the basic throttle opening degree TA0 or less. According to the above processing, when a state where a sufficient amount of internal EGR can be secured is formed, the throttle opening degree TA is throttled to achieve a state of achieving both prevention of oil rise (oil fall) and catalyst deterioration. Can be realized.

  As described above, according to the routine shown in FIG. 10, after the deceleration F / C condition is satisfied, the throttle opening TA is increased until a certain amount of internal EGR is secured (until vtt> α ° CA). While maintaining, execution of F / C can be prohibited. For this reason, according to the apparatus of the present embodiment, even in a period until vtt reaches α ° CA, an increase in oil consumption is effectively prevented, and deterioration of the upstream catalyst 38 and the downstream catalyst 40 is effectively prevented. Can be suppressed.

  Further, according to the routine shown in FIG. 10, the F / C is executed after the prohibition limit time D has elapsed after the deceleration F / C condition is satisfied, regardless of whether vtt has reached α ° CA. Can be started. For this reason, according to the system of the present embodiment, the braking force expected by the driver can be appropriately generated.

  Furthermore, according to the routine shown in FIG. 10, after the deceleration F / C condition is satisfied, the throttle opening degree TA can be gradually reduced as the actual valve timing vtt increases. For this reason, according to the apparatus of this embodiment, compared with the apparatus of Embodiment 1, prevention of oil rise (oil fall) and suppression of catalyst deterioration can be realized more effectively.

  In the second embodiment described above, the ECU 50 makes a determination of vtt> α ° CA in step 114 shown in FIG. 10, so that the “real EGR determination means” in the fifth aspect of the invention is negative. In this case, the “fuel cut prohibiting means” according to the fifth aspect of the present invention is realized by executing the processing of step 110 in FIG.

  In the second embodiment described above, the “fuel cut prohibition canceling means” according to the sixth aspect of the present invention is implemented when the ECU 50 executes the process of step 146.

Embodiment 3 FIG.
[Features of Embodiment 3]
Next, Embodiment 3 of the present invention will be described with reference to FIG. 11 and FIG.
The system of the present embodiment can be realized by causing the ECU 50 to execute a routine shown in FIG. 12, which will be described later, using the hardware configuration shown in FIG.

  As in the case of the first or second embodiment, the system of the present embodiment employs a configuration in which the throttle opening degree TA is electronically controlled based on the accelerator opening degree AA. FIG. 11A is a timing chart for explaining how the change in the accelerator opening AA is reflected in the change in the throttle opening TA in this configuration. As shown in this figure, in the system that electronically controls the throttle opening TA, after the accelerator opening AA changes, a certain delay (hereinafter referred to as Δt) occurs until the change is reflected in the throttle opening TA. Occurs).

  FIG. 11B shows a case where the target valve timing value (target VVT value) and the actual valve timing value (actual VVT value) are determined based on the accelerator opening AA. FIG. 6 is a diagram showing a comparison between the case where the determination is made based on the throttle opening degree TA. In the former case, when the accelerator opening AA is fully closed at time t0, the target VVT value rises and the actual VVT value starts to change quickly (see the solid line waveform). On the other hand, in the latter case, after the time t0, the target VVT value does not rise until the delay Δt elapses (until time t1). For this reason, the change in the actual VVT value does not occur until time t1 (see the broken line waveform).

  As in the case of the second embodiment, the apparatus of the present embodiment changes the actual valve timing vtt to the deceleration target value vt2 when the internal combustion engine 10 is decelerated, and in the course of the change, vtt becomes the determination value α °. Until CA is reached, execution of F / C is prohibited, and the throttle opening degree TA is controlled to the first target throttle opening degree ta1. In this case, the shorter the time until vtt reaches the determination value α ° CA, the earlier the F / C start time, and as a result, the fuel consumption characteristics and the engine brake response are improved.

  Therefore, in the system of the present embodiment, the accelerator opening AA itself is monitored, and when the accelerator opening AA is fully closed, it is assumed that the deceleration of the internal combustion engine 10 is requested at that time. Control to make the timing vtt coincide with the deceleration target value vt2 is started.

[Specific Processing in Embodiment 3]
FIG. 12 is a flowchart of a routine executed by the ECU 50 in the present embodiment in order to realize the above-described functions. The routine shown in FIG. 12 is the same as the routine shown in FIG. 10 except that the processing of step 150 is inserted and the position of step 140 is moved from the back of step 140 to the back of step 150. It is the same. Hereinafter, of the steps shown in FIG. 12, the same steps as those shown in FIG. 10 are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  In the routine shown in FIG. 12, following the process of step 102, it is determined whether the accelerator opening AA is fully closed (step 150). As a result, when it is determined that the accelerator opening AA is not fully closed, it is determined that the driver is not required to perform the operation accompanied by the execution of F / C. In this case, the normal operation state is continued by executing steps 106 to 110.

  On the other hand, when it is recognized that the accelerator opening AA is fully closed, it is determined by the driver that driving accompanied by execution of F / C is required. In this case, a process for setting the actual valve timing vtt to the deceleration target value vt2 is executed by the process of step 140, and thereafter, the processes after step 104 are executed.

  According to the above processing, after the driver fully closes the accelerator opening AA, the actual valve timing vtt is immediately set to the deceleration target value vt2 without waiting for the change to be reflected in the throttle opening TA. Can begin to change towards. Therefore, according to the system of the present embodiment, the F / C start response can be improved as compared with the system of the second embodiment, and as a result, the fuel consumption characteristics and the deceleration response of the internal combustion engine 10 can be improved. Can be increased.

  By the way, in the third embodiment described above, the idea of setting the timing at which the target value of the valve timing VVT is set to the deceleration target value vt2 based on the accelerator opening AA is combined with the system of the second embodiment. However, the target of the combination is not limited to the system of the second embodiment. That is, the idea may be incorporated into the system of the first embodiment.

  In the third embodiment described above, the ECU 50 electronically controls the throttle opening TA based on the accelerator opening AA, so that the “throttle opening electronic control means” in the seventh invention The “fuel cut means” according to the seventh aspect of the present invention is implemented by executing the processing of step 150 as part of the processing for determining whether or not to execute F / C.

Embodiment 4 FIG.
[Features of Embodiment 4]
Next, a fourth embodiment of the present invention will be described with reference to FIGS.
The system of the present embodiment can be realized by causing the ECU 50 to execute routines shown in FIGS. 14 to 16 to be described later, using the hardware configuration shown in FIG.

FIG. 13 is a timing chart for explaining the outline of the operation of the system of this embodiment. More specifically, FIG. 13A shows a waveform representing the execution state of F / C, FIG. 13B shows a waveform of the oxygen storage amount OSA _SC of the upstream catalyst 38, and FIG. 13C shows a downstream catalyst. The waveforms of the oxygen storage amount OSA _UF of 40 are shown.

During the execution of F / C, the gas flowing into the catalyst becomes lean. For this reason, the oxygen storage amount OSA _SC of the upstream catalyst 38 starts to increase immediately after the start of F / C, as shown in FIG. 13 (B). The oxygen storage amount OSA _SC finally converges to the maximum oxygen storage amount Cmax _SC of the upstream catalyst 38 as long as the execution of F / C is continued.

After the oxygen storage amount OSA _SC of the upstream catalyst 38 reaches Cmax _SC, when F / C is further continued, lean gas begins to blow downstream of the upstream catalyst 38, and the oxygen storage amount OSA _UF of the downstream catalyst 40 becomes _smaller. Start to increase. The oxygen storage amount OSA _UF of the downstream catalyst 40 then converges to the maximum oxygen storage amount Cmax _UF of the downstream catalyst 40 as long as F / C is continued.

  As described above, the upstream catalyst 38 and the downstream catalyst 40 are easily deteriorated by receiving the supply of lean gas in a high temperature environment. The progress of the deterioration mainly occurs in the process in which the upstream catalyst 38 and the downstream catalyst 40 each store oxygen. For this reason, after the upstream catalyst 38 and the downstream catalyst 40 saturately store oxygen, even if the lean gas is supplied in a high temperature environment, the deterioration state of the catalysts 38 and 40 hardly proceeds.

  In other words, after the start of F / C, until the downstream catalyst 40 saturately stores oxygen, the throttle opening TA is reduced to reduce the intake air amount Ga from the viewpoint of catalyst protection. However, after the downstream catalyst 40 occludes oxygen, the significance is not necessarily great.

  On the other hand, when the throttle opening degree TA is reduced during the execution of F / C, the return is forced from the state where the TA is reduced after the completion of F / C. In the present embodiment, as a precondition for reducing the TA, the actual valve timing vtt is adjusted so that a sufficient valve overlap occurs in order to avoid the intake pipe pressure PM from becoming excessively negative. Therefore, the return from F / C with the throttle opening degree TA reduced means the return from the state where the throttle opening degree TA has been reduced and a large valve overlap has occurred.

  If the F / C is terminated in a situation where a large valve overlap occurs, a large amount of internal EGR will be generated for a while after returning from the F / C. Further, when the F / C is finished with the throttle opening degree TA being reduced, the amount of fresh air flowing into the cylinder is kept small for a while after returning from the F / C. For this reason, if TA is throttled until the end of the F / C and a state in which a large valve overlap is ensured is maintained, the operating state of the internal combustion engine 10 is unstable when returning from the F / C. It is easy to become.

For this reason, if there is no benefit to throttle the throttle opening TA or to secure valve overlap, the throttle opening TA is released before the F / C ends. In addition, it is desirable to return the valve timing VVT to the timing at the time of normal operation. For the above reasons, in the present embodiment, when it is estimated that the oxygen storage amount OSA _UF of the downstream catalyst 40 has reached the maximum oxygen storage amount Cmax _UF during the execution of F / C, at that time, the throttle The throttle at the opening degree TA is released, and the valve timing VVT is returned to the normal timing.

[Specific Processing in Embodiment 4]
FIG. 14 is a flowchart of a main routine executed by the ECU 50 in the present embodiment in order to realize the above function. The routine shown in FIG. 14 is the same as the routine shown in FIG. 12 except that steps 160 to 166 are added. In FIG. 14, steps similar to those shown in FIG. 12 are denoted by the same reference numerals, and description thereof is omitted or simplified.

  That is, according to the routine shown in FIG. 14, as in the case of the routine shown in FIG. 13, the processing of step 130 is always executed during execution of the F / C. Then, according to this routine, after the process of step 130, it is determined whether or not the lean gas inflow integrated amount TGaso2 to the downstream catalyst 40 is smaller than the saturation determination value E (step 160).

  FIG. 15 is a flowchart of a routine that the ECU 50 executes to calculate the integrated lean gas inflow amount TGaso2 to the downstream catalyst 40. Note that the routine shown in FIG. 15 is a scheduled interruption routine that is repeatedly executed every predetermined time.

  In the routine shown in FIG. 15, it is first determined whether or not the deceleration F / C is being executed (step 170). As a result, when it is determined that F / C is not executed, the lean determination flag XS02L and the lean gas inflow integration amount TGaso2 are both reset to 0 (step 172).

  On the other hand, if it is determined in step 170 that the F / C is being executed, it is next determined whether or not the lean determination flag XSO2L is 0 (step 174). If it is determined that XSO2L = 0 is satisfied, it is then determined whether the output of the oxygen sensor 44 has fallen below 0.1 V after the start of F / C, that is, whether the oxygen sensor 44 has issued a lean output. (Step 176).

  When it is determined that the oxygen sensor 44 does not generate a lean output, it is determined that the lean gas has not yet started to flow out of the upstream catalyst 38, that is, the lean gas has not yet started to flow into the downstream catalyst 40. Can do. In this case, the current processing cycle is terminated without any further processing.

  On the other hand, if it is determined in step 176 that the oxygen sensor 44 is producing a lean output, it can be determined that lean gas has started to flow into the downstream catalyst 40. In this case, next, 1 is set to the lean determination flag XSO2L (step 178). Next, the latest integrated amount TGaso2 (i) is calculated by adding the intake air amount Ga generated during the execution cycle of this routine to TGaso2 (i-1) in the previous processing cycle (step S1). 180).

  Thereafter, every time the routine shown in FIG. 15 is started until F / C ends, it is determined in step 174 that XSO2L = 0 is not satisfied. As a result, the processes of steps 176 and 178 are jumped, and the process of step 180 is repeatedly executed.

  According to the above processing, after the start of F / C, the integrated value of the intake air amount Ga generated after the lean gas starts to flow downstream of the upstream catalyst 38 can be calculated as the lean gas inflow integrated amount TGaso2. .

FIG. 16 is a flowchart of a routine executed by the ECU 50 in order to calculate the saturation determination value E used in step 160. In the routine shown in FIG. 16, first, it is determined whether or not the maximum oxygen storage amount Cmax _{SC of} the upstream catalyst 38 has been calculated (step 190).

In the present embodiment, the ECU 50 can calculate the maximum oxygen storage amount Cmax _SC of the upstream catalyst 38 by a known method at an appropriate timing during the operation of the internal combustion engine 10. More specifically, the ECU 50 can calculate the Cmax _SC of the upstream catalyst 38 by executing known active control based on the output of the air-fuel ratio sensor 42 and the output of the oxygen sensor 44.

In step 190, it is determined whether or not the calculation has been completed, that is, whether or not the Cmax _{SC of the} upstream catalyst 38 has already been calculated. As a result, if it is determined that Cmax _SC has already been calculated, a saturation determination value E used for comparison with the lean gas inflow integrated amount TGaso2 is calculated based on CmaxSC (step 194).

The saturation judgment value E is set so that the value coincides with the lean gas inflow integrated amount TGaso2 necessary for causing the downstream catalyst 40 to saturately store oxygen. Here, the lean gas inflow integrated amount TGaso2 increases as the maximum oxygen storage amount Cmax _UF of the downstream catalyst 40 increases. The system of this embodiment does not have a function of directly detecting the maximum oxygen storage amount Cmax _UF . However, the maximum oxygen storage amount Cmax _UF of the downstream catalyst 40 is a value that changes as the catalyst deteriorates, like the maximum oxygen storage amount Cmax _SC of the upstream catalyst 38. For this reason, a significant correlation is recognized between these two Cmax _UF and Cmax _SC . Therefore, in this embodiment, the saturation determination value E is set based on the maximum oxygen storage amount Cmax _SC of the upstream catalyst 38 having an indirect correlation.

FIG. 17 is an example of a map that the ECU 50 refers to when setting the saturation determination value E by the above method. In step 192, the ECU 50 refers to the map shown in FIG. 17 and calculates the saturation determination value E of the lean gas inflow integrated value TGaso2 based on the maximum oxygen storage amount Cmax _SC of the upstream catalyst 38. According to this map, as the Cmax _{SC of the} upstream catalyst 38 increases, the saturation determination value E is set to a larger value.

The Cmax _{SC of the} upstream catalyst 38 is executed in an environment where a predetermined condition is satisfied during operation of the internal combustion engine 10. For this reason, the calculation may not be completed at the time when the process of step 190 is requested. In this case, a maximum possible value is set as the maximum oxygen storage amount Cmax _SC of the upstream catalyst 38 (step 194), and the process of step 192 is executed based on the maximum Cmax _SC . Based on the maximum Cmax _SC , the saturation judgment value E is set to the maximum value. According to such processing, since the calculation of Cmax _SC is not completed, it is possible to reliably prevent the saturation determination value E from being set to an excessively small value.

In step 160 shown in FIG. 14, it is determined whether or not the lean gas inflow integrated amount TGaso2 calculated as described above is smaller than the saturation determination value E set as described above. According to this determination, it is determined substantially whether the oxygen storage amount OSA _UF of the downstream catalyst 40 is smaller than the maximum oxygen storage amount Cmax _UF .

  And when establishment of TGaso2 <E is recognized, it can be judged that the downstream catalyst 40 has not occluded oxygen yet in saturation. According to the routine shown in FIG. 14, in this case, the processing cycle of this time is not performed, that is, the throttle opening TA is reduced and the large valve overlap is maintained. Is terminated.

  While oxygen is not occluded in the downstream catalyst 40 in a saturated manner, there is a benefit of reducing the throttle opening TA for protection. According to the series of processes described above, the throttle opening degree TA can be maintained while the profit exists. For this reason, according to the apparatus of this embodiment, the catalyst can be protected as in the case of the third embodiment.

  If it is determined in step 160 that TGaso2 <E is not established, the throttle opening degree TA is then controlled to the first target throttle opening degree ta1 (step 164). Next, a process for setting the actual valve timing vtt to the normal target value vt1 is executed (step 166). Note that the processing in step 164 and the processing in step 166 are the same as the processing in step 144 and the processing in step 106, respectively, so that further description is omitted here.

  According to the above processing, after oxygen is saturated and occluded in the downstream catalyst 40, that is, after the profit of reducing the throttle opening TA disappears, the valve overlap is returned to the normal value, and the throttle By opening the opening degree TA, it is possible to create a state where no oil rise (oil fall) occurs. By realizing such a state prior to the end of the F / C, the stability of the internal combustion engine 10 when returning from the F / C can be improved without any disadvantage. it can.

  By the way, in the above-described fourth embodiment, when the determination of TGaso2 <E is not established in step 160, the throttle opening degree TA is released and the valve overlap is returned to the normal value. However, the present invention is not limited to this. That is, the release of the throttle opening TA and the return of the valve overlap to the normal value may be simply performed when the F / C duration time reaches a predetermined time.

  Further, in the fourth embodiment described above, when the accumulated lean gas inflow amount TGaso2 to the downstream catalyst 40 reaches the amount (E) that saturates the downstream catalyst 40 with oxygen, the effect of reducing the throttle opening TA disappears. However, the determination method is not limited to this. That is, the determination may be made based on whether or not the cumulative intake air amount after the start of F / C can be estimated to have reached a value that saturates both the upstream catalyst 38 and the downstream catalyst 40 with oxygen. Good.

  Further, in the above-described fourth embodiment, when the F / C continues for a long time, the throttle opening degree TA is released at an appropriate timing and the valve overlap is returned to the normal time. Although incorporated into the apparatus of the third embodiment, the present invention is not limited to this. That is, the above-described processing unique to the present embodiment may be incorporated into the apparatus according to the first or second embodiment.

  In the fourth embodiment described above, the ECU 50 executes the process of step 166, so that the “EGR increase canceling means” in the eighth invention executes the process of step 164. The “reduction in weight reduction” in the invention is realized respectively.

  Further, in the above-described fourth embodiment, the “continuation time judging means” in the ninth aspect of the present invention is realized by the ECU 50 executing the process of step 160.

  Further, in the above-described fourth embodiment, the ECU 50 executes the routine shown in FIG. 15 so that the “air amount integrating means” in the tenth invention executes the processing of step 160 to execute the tenth. The “determination means” in the present invention is realized.

  Further, in the above-described fourth embodiment, the ECU 50 executes the processing of steps 190 and 194, whereby the “upstream oxygen storage capacity detecting means” in the eleventh invention executes the processing of step 192. Thus, the “setting means” in the eleventh aspect of the present invention is realized.

Embodiment 5 FIG.
[Features of Embodiment 5]
Next, a fifth embodiment of the present invention will be described with reference to FIGS.
The system of the present embodiment can be realized by causing the ECU 50 to execute routines shown in FIGS. 19, 20, and 22 described later using the hardware configuration shown in FIG.

FIG. 18 is a timing chart for explaining the outline of the operation of the system of this embodiment. More specifically, FIG. 18A is a waveform representing the execution state of F / C, FIG. 18B is a waveform of the oxygen storage amount OSA _SC of the upstream catalyst 38, and FIG. The waveforms of the oxygen storage amount OSA _UF are shown. FIG. 18D shows a waveform of the throttle opening degree TA during execution of F / C.

  Similar to the system of the fourth embodiment described above, the system of the present embodiment has the throttle opening degree TA at the time when the downstream catalyst 40 is estimated to saturately store oxygen after the start of F / C. Release the aperture. In FIG. 18D, the waveform shown between times t0 and t2 is a waveform for realizing the above function, that is, a waveform realized also in the above-described fourth embodiment.

  The system of the present embodiment sets the throttle opening TA to a third target throttle opening ta3 larger than the first target throttle opening ta1 when releasing the throttle opening TA at time t2. Thereafter, at an appropriate timing (time t3 in FIG. 18), the throttle opening TA is set to the first target throttle opening ta1.

  At time t2, the upstream catalyst 38 and the downstream catalyst 40 both store oxygen in a saturated manner. For this reason, after time t2, there is no practical benefit of suppressing the flow rate of air flowing into the catalyst. On the other hand, if the amount of air is increased, cooling of the upstream catalyst 38 and the downstream catalyst 40 can be promoted. The catalyst is deteriorated by receiving a large amount of oxygen in a high temperature environment. In other words, even in a situation where a large amount of oxygen is supplied, if the catalyst is at a low temperature, the progress of the deterioration can be suppressed. For this reason, if a large amount of circulating air is generated at the time t2 and the cooling of the upstream catalyst 38 and the downstream catalyst 40 is promoted, an advantageous situation can be created for suppressing such deterioration. .

  From the above viewpoint, the system according to the present embodiment sets the throttle opening TA to a value larger than the first target throttle opening ta1 when the downstream catalyst 40 is saturated with oxygen, as shown in FIG. 3 target throttle opening degree ta3. Since such throttle control is executed, according to the system of the present embodiment, it is possible to further suppress the deterioration of the upstream catalyst 38 and the downstream catalyst 40 as compared with the case of the fourth embodiment.

[Specific Processing in Embodiment 5]
FIGS. 19 and 20 are flowcharts of a main routine executed by the ECU 50 in the present embodiment in order to realize the above functions. This flowchart shows that steps 118, 120, 130, 144, 162, and 164 are replaced with steps 118 ', 120', 130 ', 144', 162 ', and 164', respectively, and steps 200-208. 14 is the same as the routine shown in FIG. 14 except that is added (all are shown in a shaded state). In FIG. 19 and FIG. 20, the same steps as those shown in FIG. 14 are denoted by the same reference numerals, and the description thereof is omitted or simplified.

In the present embodiment, the target value of the throttle opening degree ta, that is, the target ta is calculated by the following equation.
Target ta = basic idle opening TA0
+ First correction coefficient kfcta1−second correction coefficient kfcta2 + third correction coefficient kfcta3
... (2)
However, the third correction coefficient kfcta3 is a coefficient for greatly opening the throttle opening degree TA when the downstream catalyst 40 is saturated with oxygen.

  Steps 118 ′, 120 ′, 130 ′, 144 ′, 162 ′, and 164 ′ are each formally performed in accordance with the change of the target ta arithmetic expression from the above expression (1) to the above expression (2). , 120, 130, 144, 162 and 164. Specifically, steps 118 ′, 120 ′, and 162 ′ are obtained by adding processing for setting the third correction coefficient kfcta 3 to 0 to the processing of steps 118, 120, and 162. Steps 130 ′, 144 ′, and 164 ′ are all steps for calculating the target ta by the above equation (2) under the condition that the third correction coefficient kfcta 3 is set to 0.

  That is, the content of the processing executed in steps 118 ′, 120 ′, 130 ′, 144 ′, 162 ′ and 164 ′ is substantially executed in steps 118, 120, 130, 144, 162 and 164. The content of the process is the same. For this reason, the routine shown in FIGS. 19 and 20 is substantially the same as the routine shown in FIG. 14 except that the processing of steps 200 to 210 is added. Hereinafter, the contents of the routines shown in FIGS. 19 and 20 will be described with a focus on the description of steps 200 to 210 unique to the present embodiment.

  That is, according to the routines shown in FIGS. 19 and 20, when the execution of F / C is prohibited, the cooling flag XCOOL is set to 0 after the processing of step 110 (step 200). The cooling flag XCOOL is a flag for displaying that the upstream catalyst 38 and the downstream catalyst 40 are sufficiently cooled. During the prohibition of F / C, it is normal for the catalyst to become high temperature, so that the flag XCOOL is set to 0 here.

  According to the routines shown in FIGS. 19 and 20, while F / C is prohibited, and after the start of F / C, the condition of step 160 is satisfied, that is, F / C is started. 14 until the oxygen saturation of the downstream catalyst 40 is determined, the same processing as that when the routine shown in FIG. 14 is executed is repeated except that the processing of step 200 is executed. That is, according to the system of the present embodiment, the same operation as that of the fourth embodiment is realized during this period.

  In the routine in the present embodiment, if TGaso2 <E is not established in step 160, that is, if oxygen saturation of the downstream catalyst 40 is estimated, after kfcta2 and kfcta3 are both set to 0 in step 162 ′, It is determined whether 1 is set in the cooling flag XCOOL (step 202).

  Immediately after the first failure of the condition in step 160 is recognized, the cooling flag XCOOL is set to 0, so the condition of step 202 is not satisfied. In this case, the third correction coefficient kfcta3 is then calculated with reference to the map shown in FIG. Then, the throttle opening degree TA is controlled so that the target ta (third target throttle opening degree ta3) obtained by substituting the third correction coefficient kfcta3 into the above equation (2) is realized (step S3). 204).

  FIG. 21 shows an example of a map stored in the ECU 50 for calculating the third correction coefficient kfcta3. According to this map, the third correction coefficient kfcta3 is set to a larger value as the engine speed NE is higher, and is set to a minimum value 0 when the engine speed NE is a value close to the idle speed. The Further, according to this map, the third correction coefficient kfcta3 that is sufficiently larger than the first correction coefficient kfcta1 can be set except during idle operation. For this reason, according to the process of step 204, it is possible to create a situation in which a sufficiently large amount of intake air Ga can be circulated as compared with the intake air amount Ga for the purpose of preventing oil rise (oil fall). .

  In the series of processes shown in FIG. 20, when the process of step 204 is completed, it is next determined whether or not the cooling air integrated amount TGacool has reached the cooling determination value F (step 206). The integrated cooling air amount TGacool is an integrated value of the intake air amount Ga that circulates after the processing of step 204 is started, that is, after the throttle opening degree TA is expanded to the third target throttle opening degree ta3. On the other hand, the cooling determination value F is a value set as an air amount necessary for sufficiently cooling the upstream catalyst 38 and the downstream catalyst 40 (the setting method will be described in detail later). Therefore, according to the processing in step 206, it can be determined whether or not the upstream catalyst 38 and the downstream catalyst 40 have been sufficiently cooled to such an extent that the progress of deterioration can be suppressed.

  When it is determined that TGacool> F is not established, it can be determined that the upstream catalyst 38 and the downstream catalyst 40 have not been sufficiently cooled. In this case, after the cooling air integrated amount TGacool is updated (step 208), the actual valve timing vtt is controlled to the normal target value vt1 in step 166. In step 208, specifically, the latest integrated amount is obtained by adding the intake air amount Ga generated during the execution period of this routine to TGacool (i-1) in the previous processing cycle. A process of calculating TGacool (i) is executed.

  The processes in steps 202 to 208 and step 166 described above are repeatedly executed each time this routine is started until the cooling air integrated amount TGacool reaches the cooling determination value F as long as F / C is continued. According to such a process, after the oxygen saturation of the downstream catalyst 40 is estimated, the valve timing VVT is returned to the normal setting until the sufficient cooling of the upstream catalyst 38 and the downstream catalyst 40 is determined. A large amount of air can be circulated in the state. For this reason, according to the system of this embodiment, the upstream catalyst 38 and the downstream catalyst 40 can be effectively cooled during the execution of the F / C, and the progress of the deterioration can be effectively prevented.

  When the execution of F / C is continued until the cooling flow rate integrated value TGacool reaches the cooling determination value F, at that time (see t3 in FIG. 18), it is determined that the condition of step 206 is satisfied. In this case, following the process of step 206, 1 is set to the cooling flag XCOOL, and the cooling air integrated amount TGacool is reset to 0 (step 210). Thereafter, as a continuation of the current processing cycle, the processing subsequent to step 162 ′ is executed again. That is, in step 162 ′, after the third correction coefficient kfcta3 is reset to 0, it is determined again that XCOOL = 1.

  Here, since it is determined that XCOOL = 1 is satisfied, the process of step 164 ′ is executed next. That is, by substituting the first correction coefficient kfcta1 calculated according to the map shown in FIG. 7 and the second and third correction coefficients kfcta2 and kfcta3, both of which are set to 0, the first target is obtained. The throttle opening degree ta1 is calculated, and control for setting the throttle opening degree TA to the first target throttle opening degree ta1 is executed. Thereafter, in step 166, after the process of setting the actual valve timing vtt to the normal target value vt1 is executed, the current processing cycle is ended.

  When this routine is started after the next time, as long as the execution of F / C is continued, the processing of step 164 ′ and step 166 is repeatedly executed. As a result, execution of F / C is continued with the valve timing VVT set to the normal setting and the throttle opening TA set to the minimum opening that can avoid the oil increase (oil decrease). (See time t3 and thereafter in FIG. 18).

  If the above-described state is formed prior to the end of the F / C, it is possible to immediately return to the normal operation state by simply restarting the fuel injection from the fuel injection valve 26. For this reason, according to the system of the present embodiment, the stability of the internal combustion engine 10 at the time of return from the F / C can be sufficiently ensured as in the system of the fourth embodiment.

  FIG. 22 is a flowchart of a routine executed by the ECU 50 in order to set the cooling determination value F used in step 206 described above. In the routine shown in FIG. 22, it is first determined whether or not the catalyst temperature estimation calculation has been completed (step 220). The ECU 50 can estimate the catalyst temperature based on the operating state of the internal combustion engine 10 or the like. In step 220, it is determined whether the calculation has been completed.

  As a result of the above determination, when the estimation of the catalyst temperature is completed, a cooling determination value F is calculated based on the estimation result (step 222). Since the cooling determination value F is an air flow rate necessary for sufficiently cooling the upstream catalyst 38 and the downstream catalyst 40, it is necessary to set a larger amount as the catalyst temperature is higher.

  FIG. 23 is an example of a map of the cooling determination value F used in the present embodiment from the above viewpoint. In step 222, the ECU 50 sets the cooling determination value F by referring to this map. According to such processing, as the catalyst temperature is higher, the cooling determination value F can be set to a larger value, and the above requirement can be satisfied.

  The estimation of the catalyst temperature may not be completed when the processing of step 220 is required. In this case, the catalyst temperature is set to the lowest possible temperature (for example, 500 ° C.) (step 224), and the process of step 222 is executed based on the lowest catalyst temperature. Based on the lowest catalyst temperature, the cooling judgment value F is set to the minimum value. According to such processing, since the estimation of the catalyst temperature is incomplete, the cooling determination value F is set to an excessive value, and as a result, the upstream catalyst 38 and the downstream catalyst 40 are reliably cooled excessively. Can be prevented.

  By the way, in the above-described fifth embodiment, when the determination of TGaso2 <E is not established in step 160, the throttle opening TA is set to the opening for cooling, that is, the third target throttle opening ta3. Although it is supposed to be opened, the present invention is not limited to this. That is, the throttle opening degree TA may be simply changed to the third target throttle opening degree ta3 when the F / C duration time reaches a predetermined time.

  In the fifth embodiment described above, the process for cooling the catalyst at the stage where the downstream catalyst 40 has saturatedly occluded oxygen is incorporated in the apparatus of the fourth embodiment. It is not limited to. That is, the above-described processing unique to the present embodiment may be incorporated into any of the devices of the first to third embodiments.

  In the above-described fifth embodiment, the ECU 50 executes the process of step 204, so that the “cooling flow rate realization means” in the twelfth aspect of the invention executes the process of step 164 ′. Each of the “flow rate changing means” in the present invention is realized.

  In the fifth embodiment described above, the ECU 50 executes the process of step 220 or 224, so that the “catalyst temperature detection estimation means” in the thirteenth aspect of the invention executes the process of step 222. The “cooling time setting means” in the thirteenth aspect of the invention is realized.

Embodiment 6 FIG.
[Features of Embodiment 6]
Next, a sixth embodiment of the present invention will be described with reference to FIGS.
The system of the present embodiment can be realized by causing the ECU 50 to execute routines shown in FIGS. 24 and 27 to be described later using the hardware configuration shown in FIG.

  The system according to the present embodiment is different from the first to fifth embodiments in that the valve timing VVT is changed so that the valve overlap increases, that is, the internal EGR amount increases during the execution of the F / C. It is the same. Here, for convenience of explanation, it is assumed that the variable valve mechanism 32 advances the valve opening timing of the intake valve 28 to increase the valve overlap.

  When the variable valve mechanism 32 is operated in the advance direction during the execution of the F / C, in order to maintain the state of the internal combustion engine stably at the time of return from the F / C, the variable valve mechanism 32 is simultaneously restored. It is necessary to properly reduce the internal EGR amount by canceling the advance angle. At this time, if the responsiveness of the variable valve mechanism 34 is slow and the advance angle state is maintained, the operation state of the internal combustion engine becomes unstable until the advance angle is released.

  In order to prevent such a situation from occurring, the system according to the present embodiment, prior to driving the variable valve mechanism 32 in the advance direction, more specifically, the operating speed of the variable valve mechanism 32, more specifically, The operating speed when the variable valve mechanism 32 operates in the retarding method is detected. In addition, the system of the present embodiment sets the advance amount of the variable valve mechanism 32 during F / C based on the operating speed detected as described above. That is, when the operating speed of the variable valve mechanism 32 is fast, the advance amount during F / C is set to be large, and conversely, when the operating speed is slow, the advance amount during F / C is set. We decided to set it to a small value. According to such a setting, regardless of the operating speed of the variable valve mechanism 32, the advance amount of the variable valve mechanism 32 is always released promptly when returning from the F / C, so that the internal combustion engine is stabilized. It is possible to realize a state where the vehicle can be driven quickly.

[Specific Processing in Embodiment 6]
FIG. 24 is a flowchart of a first routine executed by the ECU 50 in order to realize the above function. More specifically, this routine detects an operating speed when the variable valve mechanism 32 operates in the retarding direction, and based on the operating speed, the correction coefficient kdvt2 of the valve timing VVT and the throttle opening degree are detected. This is for calculating the correction coefficient kfcta2.

  In the routine shown in FIG. 24, first, the engine speed NE is taken in (step 230). Next, it is determined whether or not the engine speed NE is higher than the determination speed a (step 232). The variable valve mechanism 32 is driven by the hydraulic pressure of the internal combustion engine. For this reason, the operating speed of the variable valve mechanism 32 has different values depending on the level of the engine speed NE.

  In the system according to the present embodiment, it is desired that the variable valve mechanism 32 is advanced by a large angle during F / C in the high rotation region as compared to during F / C in the low rotation region. For this reason, when examining whether or not the variable valve mechanism 32 can return to an appropriate state upon return from the F / C, what operating speed the variable valve mechanism 32 exhibits in the high rotation region is shown. It is appropriate to see.

  The determination rotational speed a used in step 232 is a value for determining whether or not the internal combustion engine is operating in a high rotational speed region (for example, 300 rpm or higher). Therefore, if the determination is negative, it is determined that the current operating state is not a state in which the operating speed of the variable valve mechanism 34 should be detected, and the current process is immediately terminated thereafter.

  On the other hand, if NE> a is established in step 232, it can be determined that the condition for detecting the operating speed of the variable valve mechanism 32 is satisfied as far as the engine speed NE is concerned. In this case, first, the actual valve timing vtt is captured (step 234), and then it is determined whether or not the captured vtt is greater than the determination value b (step 236).

  In order to accurately detect the operating speed of the variable valve mechanism 32, it is necessary to operate the variable valve mechanism 32 to some extent. That is, in order to detect the operating speed of the variable valve mechanism 32 in the retard direction, it is necessary that the variable valve mechanism 32 be displaced in the advance direction to some extent.

  If it is determined in step 236 that vtt> b is not satisfied, it is determined that the precondition is not satisfied, and the current process is immediately terminated thereafter. On the other hand, when the establishment of vtt> b is recognized, it can be determined that the condition for detecting the operating speed is satisfied as far as the advance amount of the variable valve mechanism 32 is concerned. In this case, it is next determined whether or not the valve timing fully-closed control is requested (step 238).

  The variable valve mechanism 32 is advanced in the advance direction so that a certain degree of valve overlap occurs in a situation where the engine speed NE is secured to some extent and the throttle opening degree TA is secured to some extent. Driven. The variable valve mechanism 32 is driven so that the valve overlap disappears when the internal combustion engine is lightly loaded. For this reason, for example, when the throttle valve 18 is closed during acceleration or high-speed traveling, a change from medium to high load to light load is recognized, and the variable valve mechanism 32 is It will be driven to the state where the advance angle is released. Then, when the throttle fully closed state is continued and it is determined that the F / C condition is satisfied, the F / C described above is started through the above change.

  As described above, in the system according to the present embodiment, when the change from the medium to high load to the light load is recognized, the variable valve mechanism 32 is instructed to cancel the advance angle. When this release is instructed, the variable valve mechanism 32 operates in the retard direction at the maximum speed in order to quickly release the advanced state. In the present specification, the control for operating the variable valve mechanism 32 in the retarding direction as described above is referred to as “fully closed control”.

  In the routine shown in FIG. 24, if it is determined in step 238 that a request for full-closed control has not occurred, it can be determined that an opportunity to detect the operating speed of the variable valve mechanism 32 has not occurred. In this case, the current process is immediately terminated thereafter. On the other hand, if it is determined that a request for the fully closed control has occurred, then the closing speed Δvtc of the variable valve mechanism 32 is taken in (step 240).

  The closing speed Δvtc is an operation amount per unit time generated in the variable valve mechanism 32 after the fully closing control is started. In step 240, specifically, the operating position of the variable valve mechanism 32 is detected at a predetermined sampling cycle by a sensor built in the variable valve mechanism 32. Then, the closing speed Δvtc is calculated based on the sampling period and the change amount of the operating position.

  When the above processing is completed, 1 is then set to the closing speed detected flag XΔVTC (step 242). Next, a correction coefficient kdvt2 corresponding to the closing speed Δvtc is calculated (step 244).

  The correction coefficient kdvt2 is a coefficient for correcting the target value vt2 at the time of deceleration of the valve timing VVT. FIG. 25 shows an example of a map stored in the ECU 50 for calculating the correction coefficient kdvt2. According to this map, the correction coefficient kdvt2 is set as a function of the closing speed Δvtc. Specifically, the correction coefficient kdvt2 is set to approach the minimum value 0 as the closing speed Δvtc decreases, and to approach the maximum value 1.0 as the closing speed Δvtc increases. The method of correcting the target value vt2 using the correction coefficient kdvt2 and the physical meaning of the target value vt2 obtained as a result will be described in detail later with reference to FIG.

  Next, according to the routine shown in FIG. 24, the correction coefficient kdta2 corresponding to the correction coefficient kdvt2 is calculated (step 246). The correction coefficient kdta2 calculated here is a coefficient for correcting the second correction coefficient kfcta2 that determines the throttle amount to be given to the throttle opening degree TA during F / C.

  FIG. 26 shows an example of a map stored in the ECU 50 for calculating the correction coefficient kdta2. According to this map, the correction coefficient kdta2 is set as a function of the correction coefficient kdvt2 set in step 244. Specifically, the correction coefficient kdta2 is set so as to show a substantially proportional relationship with the correction coefficient kdvt2. For this reason, the correction coefficient kdta2 calculated here also approaches the minimum value 0 as the closing speed Δvtc of the variable valve mechanism 32 is slow, and the maximum value as the speed Δvtc is fast, similarly to the correction coefficient kdvt2. It is set to approach 1.0. Note that the method of correcting the throttle amount (second correction coefficient kfcta2) of the throttle opening TA using the correction coefficient kdta2 and the physical meaning of the second correction coefficient kfcta2 obtained as a result refer to FIG. This will be described in detail later.

  FIG. 27 is a flowchart of a routine executed by the ECU 50 in this embodiment in order to control the variable valve mechanism 32 and the throttle valve 18. This routine is substantially the same as the routine shown in FIG. 3 except that the processing in steps 250 to 260 is inserted at an appropriate location. Hereinafter, of the steps shown in FIG. 27, the same steps as those shown in FIG. 3 are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  According to the routine shown in FIG. 27, if the establishment of the F / C condition is confirmed in step 104, it is next determined whether or not 1 is set in the closing speed detected flag XΔVTC (step 250). . As a result, when it is determined that XΔVTC = 1 is not established, it can be determined that the closing speed Δvtc of the variable valve mechanism 32 has not been detected yet.

  When the closing speed Δvtc is known, the system of the present embodiment calculates an advance amount that can be quickly extinguished by the closing speed Δvtc, and sets the calculated value as a target VVT (vt2) for deceleration To do. However, while the closing speed Δvtc is unknown, such target value vt2 cannot be set appropriately. Therefore, if it is determined in step 250 that XΔVTC is not set to 1, the target VVT (vt2), that is, the advance amount to be given to the variable valve mechanism 32 during F / C is the minimum. The value is 0.

  When the target VVT (vt2) is set to the minimum value 0, the valve overlap does not occur, so the internal EGR amount can be suppressed to a small amount. In this case, if the throttle opening degree TA is closed excessively, the pressure in the intake passage becomes excessively negative, causing the problem of oil increase or oil decrease. For this reason, when the process of step 252 is executed, the processes of steps 116 and 118 are executed in order to correct the throttle opening degree TA to the opening side from the basic idle opening degree.

  On the other hand, when it is determined in step 250 that the closing speed detected flag XΔVTC is set to 1, first, the target VVT (vt2) at the time of deceleration is calculated by the processing of step 112 (hereinafter referred to as here). The calculated value is set as “vt2 reference value”), and then the correction coefficient kdvt2 is fetched (step 254).

  In the process of step 112, as in the case of the first embodiment, according to the map shown in FIG. 5, the valve timing required for generating a sufficient EGR amount during the F / C (in this embodiment, the variable valve The advance amount of the mechanism 32) is calculated as vt2. Further, according to the processing in step 254, the correction coefficient kdvt2 calculated in step 244 shown in FIG. 24 is captured.

In the routine shown in FIG. 27, the target VVT (vt2) to be used in the current processing cycle is calculated by substituting the reference value of vt2 and the correction coefficient kdvt2 into the right side of the following equation (step 256).
vt2 = vt2 * kdvt2 (3)

  As described above, the correction coefficient kdvt2 is a coefficient that approaches the maximum value 1.0 as the closing speed Δvtc increases (see FIG. 25). Therefore, according to the above equation (3), the target VVT (vt2) is set to a value closer to the reference value of vt2 as the closing speed Δvtc is faster, and to a value closer to the minimum value 0 as the closing speed Δvtc is slower. Is done.

  In the routine shown in FIG. 27, later, in step 128, the variable valve mechanism 32 is controlled so that the actual VVT matches the target VVT (vt2). As a result, the advance amount given to the variable valve mechanism 32 during F / C increases as the closing speed Δvtc increases, and decreases as the closing speed Δvtc decreases. For this reason, according to the system of the present embodiment, even when the variable valve mechanism 32 exhibits any closing speed, the advance angle of the variable valve mechanism 32 is always quickly released upon return from the F / C. It is possible to create a situation where the internal combustion engine can operate stably.

In addition, according to the routine shown in FIG. 27, after the second correction coefficient kfcta2 is calculated by the process of step 122 (hereinafter, the value calculated here is referred to as “reference value of kfcta2”), it is shown in FIG. The correction coefficient kdta2 calculated in step 246 is fetched (step 258). Next, the second correction coefficient kfcta2 to be used in the current processing cycle is calculated by substituting the reference value of the second correction coefficient kfcta2 and the correction coefficient kdta2 into the right side of the following equation (step 260).
kfcta2 = kfcta2 * kdta2 (4)

  As described above, the correction coefficient kdta2 has a substantially proportional relationship with the correction coefficient kdvt2 (see FIG. 26). Therefore, according to the above equation (4), the second correction coefficient kfcta2 becomes closer to the reference value of kfcta2 as the correction coefficient kdvt2 approaches 1.0, and as the correction coefficient kdvt2 approaches the minimum value 0. The value is close to the minimum value 0. In other words, the second correction coefficient kfcta2 becomes a value closer to the maximum value 1.0 as the closing speed Δvtc is faster and a larger advance amount vt2 is set, and the closing speed Δvtc is slower and the advance amount vt2 is smaller. Is set to a value closer to the minimum value 0.

  In the routine shown in FIG. 27, calculation of target ta and control of throttle opening degree TA are performed later in step 130. The calculation of the target ta is performed according to the above equation (1), that is, according to the arithmetic expression “target ta = basic idle opening degree TA0 + first correction coefficient kfcta1−second correction coefficient kfcta2”. When the process of step 260 is executed, the first correction coefficient kfcta1 is set to 0 (see step 120). In this case, the target ta is a value obtained by subtracting the second correction coefficient kfcta2 from the basic idle opening degree TA0. In other words, in this case, as the advance amount vt2 during F / C is set to a larger value, the target ta becomes a value that is greatly reduced from the basic idle opening TA0, while the advance amount vt2 is reduced to a smaller value. The target ta becomes a value closer to the basic idle opening TA0 as the value is set.

  When the advance amount vt2 is large, even if the target ta is greatly reduced, the intake negative pressure does not become so large, so that the oil rise and oil fall can be sufficiently suppressed. On the other hand, even when the advance amount vt2 cannot be sufficiently ensured, if the target ta is reduced, oil rise and oil fall can be prevented. According to the setting of the target ta described above, it is possible to appropriately create these situations according to the value of the advance amount vt2. For this reason, according to the system of the present embodiment, while the advance amount vt2 is adjusted in accordance with the operating speed of the variable valve mechanism 32, as in the case of the first to fifth embodiments, the oil increase and oil decrease are reduced. It is possible to achieve both prevention and protection of the catalyst.

  By the way, in the above-described sixth embodiment, for convenience of explanation, a valve overlap is generated by advancing the variable valve mechanism 32 on the intake side, and according to the operating speed of the variable valve mechanism 32, However, the present invention is not limited to this. That is, the valve overlap may be generated by retarding the variable valve mechanism 34 on the exhaust side. In that case, the same effect as in the sixth embodiment can be realized by determining the amount of retardation at that time in accordance with the operating speed of the variable valve mechanism 34.

  In the sixth embodiment described above, the mechanism for generating EGR during F / C is limited to the variable valve mechanism 32 (or 34), but the mechanism is not limited to this. That is, the mechanism for generating EGR during F / C may be an external EGR mechanism including an EGR valve or the like. In this case, it is possible to obtain the same effect as in the sixth embodiment by determining the operation amount of the EGR valve during the F / C based on the operation speed of the EGR valve.

  In the above-described sixth embodiment, the closing speed Δvtc of the variable valve mechanism 32 is measured after waiting for the fully closed control (see step 238) to be executed. It is not limited to. That is, the fully closed control may be forcibly executed when the measurement of the closing speed Δvtc is required.

  In the sixth embodiment described above, the variable valve mechanism 32 corresponds to the “EGR variable mechanism” in the fourteenth aspect of the invention, and the ECU 50 executes the process of step 240 to execute the fourteenth aspect. The “actuation speed setting means” in the fourteenth aspect of the present invention is realized by executing the processing of step 244 and steps 254 and 256 in the “operation speed detection means” of the present invention.

  In the sixth embodiment described above, the “aperture amount setting means” in the fifteenth aspect of the present invention is realized by the ECU 50 executing the processing of step 246 and steps 258 and 260, respectively.

Embodiment 7 FIG.
[Features of Embodiment 7]
Next, Embodiment 7 of the present invention will be described with reference to FIGS.
The system of the present embodiment can be realized by causing the ECU 50 to execute a routine shown in FIG. 28 described later instead of the routine shown in FIG. 24 in the system of the sixth embodiment described above.

  The system of the sixth embodiment described above permits measurement of the closing speed Δvtc of the variable valve mechanism 32 when the engine speed NE is higher than the determination speed a (see step 230 above). However, according to such a method, the closing speed Δvtc cannot be measured as long as the internal combustion engine continues to operate in the low rotation range, and as a result, the advance amount vt2 to be realized during F / C is set correctly. The situation of being unable to continue continues.

  Incidentally, since the variable valve mechanism 32 uses hydraulic pressure as a power source, the closing speed Δvtc of the variable valve mechanism 32 shows a significant correlation with the engine speed NE. If this correlation is known, it is possible to convert the closing speed Δvtc0 measured under an arbitrary engine speed NE to the closing speed Δvtc in the high speed region. If the closing speed Δvtc is estimated by such conversion, it is possible to obtain the closing speed Δvtc in the high rotation region without waiting for the internal combustion engine to reach the high rotation region. Therefore, the system according to the present embodiment estimates the closing speed Δvtc by the above method immediately after the internal combustion engine is started.

[Specific Processing in Embodiment 7]
FIG. 28 is a flowchart of a routine executed by the ECU 50 in order to realize the above function. This routine is the same as the routine shown in FIG. 24 except that steps 230 and 232 are omitted and step 240 is replaced with steps 270 to 276. Of the steps shown in FIG. 28, the same steps as those shown in FIG. 24 are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  That is, according to the routine shown in FIG. 28, whether the sufficient advance amount vtt is generated or the request for the fully closed control is generated regardless of whether the engine speed NE exceeds the determination speed a. Are sequentially determined (steps 234 to 238). If these conditions are satisfied, the closing speed of the variable valve mechanism 32 is measured at that time (step 270). Hereinafter, the closing speed measured here is referred to as “reference closing speed Δvtc0”.

Next, the current engine speed NE, that is, the engine speed NE when the reference closing speed Δvtc0 is measured is taken in (step 272). Next, a VVT retardation correction coefficient knee is calculated based on the NE (step 274). Thereafter, the reference closing speed Δvtc0 and the VVT retardation correction coefficient kne are substituted into the right side of the following equation to calculate the closing speed Δvtc in the high rotation region (step 276).
Δvtc = Δvtc0 * kne (5)

  FIG. 29 is a map of the correction coefficient kne stored in the ECU 50. In this map, the correction coefficient kne is defined as a function of the engine speed NE at the time when the reference closing speed Δvtc0 is measured. More specifically, the correction coefficient kne is determined so as to increase as the engine speed NE at that time decreases, and to converge to the minimum value 1.0 as the engine speed NE at that time increases.

  In step 274, the correction coefficient kne is set according to the map shown in FIG. As a result, if the reference closing speed Δvtc is measured in the low rotation region, the correction coefficient kne is set to a large value. If the reference speed Δvtc is measured in the high rotation region, the correction coefficient kne is set to a value close to 1.0. According to these correction coefficients kne, the reference closing speed Δvtc0 can be appropriately converted to the closing speed Δvtc in the high rotation region.

  As described above, according to the routine shown in FIG. 28, it is possible to appropriately calculate the closing speed Δvtc in the high speed region without waiting for the engine speed NE to exceed the determined speed a. For this reason, according to the system of the present embodiment, it is possible to sufficiently shorten the period until the state in which the advance amount vt2 in the F / C can be properly set is established after the internal combustion engine is started.

  In the seventh embodiment described above, the ECU 50 executes the process of step 270, whereby the “operation speed measuring means” in the seventeenth aspect of the invention executes the process of step 272. The “conversion means” according to the seventeenth aspect of the present invention is realized by executing the processing of steps 274 and 276 by the “rotational speed storage means” according to the invention.

Embodiment 8 FIG.
[Features of Embodiment 8]
Next, an eighth embodiment of the present invention will be described with reference to FIG. 30 and FIG.
The system of the present embodiment adds an oil temperature sensor for detecting the oil temperature THO of the internal combustion engine to the system of the above-described sixth embodiment, and in that system, the ECU 50 is described later in place of the routine shown in FIG. This can be realized by executing the routine shown in FIG.

  In the system of the seventh embodiment described above, the reference closing speed Δvtc0 measured under an arbitrary engine speed NE is converted by the correction coefficient kne in consideration of the influence of the engine speed NE on the closing speed Δvtc. Thus, the closing speed Δvtc in the high rotation region is estimated. By the way, the operating speed of the variable valve mechanism 32 is greatly influenced by the oil temperature as well as the engine speed NE.

  That is, since the variable valve mechanism 32 uses hydraulic pressure as a power source, it shows a significant correlation with the hydraulic pressure. The hydraulic pressure of the internal combustion engine is different if the oil temperature is different even if the engine speed NE is the same. Furthermore, there is a portion that slides in response to the supply of lubricating oil inside the variable valve mechanism 32. The friction of the lubrication portion changes as the viscosity of the lubricating oil changes as the oil temperature changes. For these reasons, the closing speed Δvtc of the variable valve mechanism 32 is greatly affected by the oil temperature.

  Therefore, the system according to the present embodiment considers the influence of the oil temperature in addition to the influence of the engine speed NE when calculating the closing speed Δvtc of the variable valve mechanism 32. Hereinafter, with reference to FIG. 30 and FIG. 31, the content of the specific process for implement | achieving said function is demonstrated.

[Specific Processing in Eighth Embodiment]
FIG. 30 is a flowchart of a routine executed by the ECU 50 in the present embodiment in order to calculate the correction coefficient kdvt2 for correcting the advance amount vt2 and the correction coefficient kdta2 for correcting the throttle amount of the throttle opening TA. This routine is the same as the routine shown in FIG. 28 except that steps 280 to 294 are inserted at appropriate positions. Note that among the steps shown in FIG. 30, the same steps as those shown in FIG. 28 are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  According to the routine shown in FIG. 30, it is first determined whether or not the oil temperature detected flag XTHO is 0 (step 280). The oil temperature detected flag XTHO is a flag that is set to 0 after initialization of the internal combustion engine, and is set to 1 when the oil temperature THO is detected together with the detection of the reference closing speed Δvtc0. Therefore, immediately after starting the internal combustion engine, it is determined that XTHO = 0.

  If the establishment of XTHO = 0 is recognized, the processing such as detection of the reference closing speed Δvtc0, taking in the engine speed NE, and calculation of the correction coefficient kne is sequentially executed (steps 234 to 238 and step). 270-274). When these processes are completed, the oil temperature THO at the time when the reference closing speed Δvtc0 is detected is acquired (step 282). Further, the first VVT retardation correction coefficient ktho1 is calculated based on the oil temperature THO (step 284). The ktho1 calculation method will be described in detail later.

When these processes are completed, 1 is set to the oil temperature detected flag XTHO (step 286). Next, by substituting the reference closing speed Δvtc0 and the VVT retardation correction coefficient kne into the right side of the following equation, the closing speed in the high rotation region based on the current oil temperature THO (hereinafter referred to as “first closing speed Δvtc1”). Is calculated (step 288).
Δvtc1 = Δvtc0 * kne (6)

  Thereafter, the processing of the flag XΔVTC, the setting processing of the correction coefficients kdvt2, kdta2 (steps 278, 244, 246) and the like are executed, and then the current routine is terminated.

  The routine shown in FIG. 30 is repeatedly started at a predetermined execution cycle after the internal combustion engine is started. When this routine is started after calculating the first closing speed Δvtc1, it is determined in step 280 that XTHO = 0 is not satisfied. In this case, first, the oil temperature THO at that time is detected (step 290).

Next, a second VVT retardation correction coefficient ktho2 is calculated based on the detected oil temperature THO (step 292). Thereafter, the closing speed Δvtc is calculated according to the following equation (step 294), and the correction coefficients kdvt2 and kdta2 are calculated based on the closing speed Δvtc calculated here (steps 244 and 246).
Δvtc = Δvtc1 * ktho2 / ktho1 (7)

  FIG. 31 shows a map stored in the ECU 50 for calculating the first and second VVT retardation correction coefficients ktho1 and ktho2. The map shown in FIG. 31 defines the relationship between the VVT retardation correction coefficient ktho and the oil temperature THO. In step 284, the ECU 50 reads the correction coefficient ktho corresponding to the oil temperature THO acquired in step 282 from the map shown in FIG. 31, and sets the value as the first VVT retardation correction coefficient ktho1. In step 292, the correction coefficient ktho corresponding to the oil temperature THO acquired in step 290 is read from the map shown in FIG. 31, and the value is set as the second VVT retardation correction coefficient ktho2.

  According to the map shown in FIG. 31, the correction coefficient ktho is a value near the maximum value of 1.0 when the oil temperature THO is around 80 ° C., and the oil temperature THO increases from 80 ° C. to the high temperature side or low temperature side. The value is set so as to become smaller as the shift is performed. The hydraulic pressure that is the power source of the variable valve mechanism 32 decreases as the viscosity of the lubricating oil decreases as the oil temperature increases. On the other hand, the friction of the variable valve mechanism 32 increases as its viscosity increases as the oil temperature decreases. For this reason, the operating speed of the variable valve mechanism 32, that is, the closing speed Δvtc shows an increase / decrease tendency similar to the correction coefficient ktho shown in FIG. 31 with respect to the oil temperature.

  Therefore, “ktho2 / ktho1” included in the right side of the above equation (7) physically indicates the operating speed when the second VVT retardation correction coefficient ktho2 is detected and the first VVT retardation correction. This is equivalent to the ratio with the operating speed when the coefficient ktho1 is detected. Therefore, according to the equation (7), the closing speed Δvtc at the time when the second VVT retardation correction coefficient ktho2 is measured can be accurately calculated.

  As described above, according to the routine shown in FIG. 30, the first closing speed Δvtc1 is measured under an arbitrary engine speed NE and an arbitrary oil temperature, and the value Δvtc1 is set to a ratio of “ktho2 / ktho1”. By correcting with, the closing speed Δvtc at an arbitrary timing can be accurately calculated. Therefore, according to the system of the present embodiment, the time required for obtaining the closing speed Δvtc can be made sufficiently short as in the case of the seventh embodiment, and compared with the case of the seventh embodiment. Thus, it is possible to further improve the setting accuracy of the advance amount vt2 in F / C.

  By the way, in the above-described eighth embodiment, the oil temperature itself is detected in order to take into account the effect of the oil temperature on the closing speed Δvtc, but the basis for the correction is not limited to the oil temperature. Absent. For example, a similar function can be realized by using the cooling water temperature THW of the internal combustion engine instead of the oil temperature THO.

  In the above-described eighth embodiment, when the ECU 50 executes the process of step 270 shown in FIG. 30, the “operation speed measuring means” in the eighteenth aspect of the invention executes the process of step 280. The “oil temperature storage means” in the eighteenth aspect of the invention executes the process of step 292, so that the “oil temperature detection means” of the eighteenth aspect of the invention executes the process of step 294, thereby The “conversion means” in the invention is realized respectively.

It is a figure for demonstrating the structure of Embodiment 1 of this invention. 5 is a timing chart for explaining operations realized in the first embodiment of the present invention when F / C is executed in an environment where the engine speed NE is sufficiently high. It is a flowchart of the main routine performed in Embodiment 1 of the present invention. 4 is a map of a normal target value vt1 referred to in the routine shown in FIG. 4 is a map of a deceleration target value vt2 referred to in the routine shown in FIG. FIG. 4 is a map of determination values α referred to in the routine shown in FIG. 3. FIG. It is a map of the 1st correction coefficient kfcta1 referred in the routine shown in FIG. It is a map of the 2nd correction coefficient kfcta2 referred in the routine shown in FIG. It is a timing chart for demonstrating operation | movement of Embodiment 2 of this invention. It is a flowchart of the main routine performed in Embodiment 2 of the present invention. It is a timing chart for demonstrating the characteristic of Embodiment 3 of this invention. It is a flowchart of the main routine performed in Embodiment 3 of the present invention. It is a timing chart for demonstrating operation | movement of Embodiment 4 of this invention. It is a flowchart of the main routine performed in Embodiment 4 of this invention. It is a flowchart of the routine performed in order to calculate lean gas inflow integration amount TGaso2 in Embodiment 4 of this invention. It is a flowchart of the routine performed in order to calculate the saturation determination value E in Embodiment 4 of this invention. It is a map of the saturation judgment value E referred in the routine shown in FIG. It is a timing chart for demonstrating the operation | movement of Embodiment 5 of this invention. It is a flowchart (the 1) of the main routine performed in Embodiment 5 of this invention. It is a flowchart (the 2) of the main routine performed in Embodiment 5 of this invention. 21 is a map of a third correction coefficient kfcta3 referred to in the routine shown in FIG. It is a flowchart of the routine performed in order to calculate the cooling determination value F in Embodiment 5 of this invention. It is a map of the cooling determination value F referred in the routine shown in FIG. It is a flowchart of the routine performed in order to calculate a correction coefficient in Embodiment 6 of this invention. FIG. 25 is a map referred to for calculating a correction coefficient kdvt2 in the routine shown in FIG. 24. FIG. FIG. 25 is a map referred to for calculating a correction coefficient kdta2 in the routine shown in FIG. 24. FIG. It is a flowchart of the main routine performed in Embodiment 6 of this invention. It is a flowchart of the routine performed in order to calculate a correction coefficient in Embodiment 7 of this invention. FIG. 29 is a map referred to for calculating a correction coefficient kne in the routine shown in FIG. 28. FIG. It is a flowchart of the routine performed in order to calculate a correction coefficient in Embodiment 8 of this invention. FIG. 31 is a map referred to for calculating first and second VVT retardation correction coefficients ktho1 and ktho2 in the routine shown in FIG. 30. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 12 Intake passage 14 Exhaust passage 38 Upstream catalyst 40 Downstream catalyst 42 Air-fuel ratio sensor 44 Oxygen sensor 50 ECU (Electronic Control Unit)
F / C fuel cut
PM Intake pipe pressure
EGR exhaust gas recirculation
TA throttle opening
TA0 Basic idle opening
NE engine speed
Ga intake air volume
kl Load factor
THO oil temperature
kfcta1 First correction factor
kfcta2 Second correction factor
kfcta3 Third correction factor
VVT valve timing
vtt Actual valve timing
vt1 Normal target value
vt2 Target value for deceleration (exhaust valve retard amount or intake valve advance amount)
ta1 First target throttle opening
ta2 Second target throttle opening
ta3 Third target throttle opening α judgment value β second judgment value
TGaso2 Integrated lean gas inflow
TGacool Cooling air accumulated amount
AF / C start speed
BF / C end rotation speed
CF / C prohibited time
D Prohibition limit time
E Saturation judgment value
F Cooling judgment value Δvtc Closing speed Δvtc1 First closing speed (closing speed under any oil temperature)
kdvt2 Correction factor for correcting the target VVT
kdta2 Correction factor for correcting the throttle opening amount
kne Correction factor to absorb differences in engine speed
ktho1 First VVT retard correction factor
ktho2 Second VVT retardation correction factor

Claims (20)

Fuel cut means for performing fuel cut during deceleration of the internal combustion engine;
EGR variable mechanism that operates to change the exhaust gas recirculation amount,
The fuel cut at high engine speed, so that the exhaust gas recirculation amount as compared with the fuel cut under low engine speed becomes a large amount, and controls the EGR adjustment mechanism based on the engine speed EGR control means,
A variable intake air amount mechanism that operates to change the intake air amount;
The fuel cut at high engine speed, so that the intake air amount as compared with the fuel cut under low engine speed is reduced, the intake air amount control means that controls the intake air quantity variable mechanism When,
A control device for an internal combustion engine, comprising: An actual EGR determination means for determining whether or not an actual value of the exhaust gas recirculation amount exceeds a determination value;
The intake air amount control means waits until the actual value of the exhaust gas recirculation amount exceeds a judgment value after fuel cut is started under a high engine speed, and controls to reduce the intake air amount 2. The control apparatus for an internal combustion engine according to claim 1, further comprising control delay means for starting the engine. The EGR variable mechanism includes a variable valve mechanism that varies a valve overlap period in which an intake valve opening period and an exhaust valve opening period overlap,
The EGR control means includes VVT control means for driving the variable valve mechanism to increase or decrease the internal exhaust gas recirculation amount,
The internal combustion engine according to claim 2, wherein the actual EGR determination means determines whether or not an actual value of the exhaust gas recirculation amount exceeds a determination value based on a state of the variable valve mechanism. Engine control device.   The intake air amount control means sets an intake air amount equal to or greater than that at the start of fuel cut until the actual value of the exhaust gas recirculation amount exceeds a determination value after the fuel cut is started at a high engine speed. 4. The control apparatus for an internal combustion engine according to claim 2, further comprising means for maintaining. Actual EGR determination means for determining whether or not the actual value of the exhaust gas recirculation amount exceeds a determination value;
Fuel cut prohibiting means for prohibiting execution of fuel cut until the actual value of the exhaust gas recirculation amount exceeds a determination value after the fuel cut execution condition is satisfied;
The control device for an internal combustion engine according to any one of claims 1 to 4, further comprising:   6. The internal combustion engine according to claim 5, further comprising a fuel cut prohibition canceling unit that cancels the prohibition of execution of the fuel cut when a fuel cut prohibition limit period has elapsed after the fuel cut execution condition is satisfied. Control device. With throttle opening electronic control means for electronically controlling the throttle opening based on the accelerator opening,
The internal combustion engine control according to any one of claims 1 to 6, wherein the fuel cut means determines whether or not a fuel cut execution condition is satisfied based on the accelerator opening. apparatus. EGR increase release means for releasing the increase correction of the exhaust gas recirculation amount by the EGR control means when the fuel cut duration reaches a predetermined time;
A reduction release means for releasing the reduction correction of the intake air amount by the intake air amount control means when the fuel cut duration time reaches the predetermined time;
The control apparatus for an internal combustion engine according to any one of claims 1 to 7, further comprising:   After the start of the fuel cut, it further comprises duration determination means for determining that the duration has reached the predetermined time when it is estimated that the catalyst arranged in the exhaust passage of the internal combustion engine has fully occluded oxygen. The control apparatus for an internal combustion engine according to claim 8. The catalyst includes an upstream catalyst and a downstream catalyst arranged in series,
A downstream oxygen sensor disposed downstream of the upstream catalyst;
The duration determination means is
An air amount integrating means for calculating an integrated intake air amount from the time when the output of the downstream oxygen sensor becomes a lean output after the start of fuel cut;
10. A determination unit that determines that the duration has reached the predetermined time when the accumulated intake air amount reaches a value that allows the downstream catalyst to fully store oxygen. The internal combustion engine control device described. Upstream oxygen storage capacity detection means for detecting the oxygen storage capacity of the upstream catalyst;
A setting means for setting a value for fully storing oxygen in the downstream catalyst based on an oxygen storage capacity of the upstream catalyst;
The control apparatus for an internal combustion engine according to claim 10, further comprising: Cooling flow rate realization means for controlling the intake air amount to a cooling target flow rate that is larger than the flow rate before the start of the fuel cut when the fuel cut duration time reaches the predetermined time;
When the target cooling flow rate is maintained for a predetermined cooling time while the fuel cut is continued, the intake air amount is larger than the flow rate before the start of the fuel cut, and compared with the target cooling flow rate. And a flow rate changing means for controlling the flow rate to be small,
The control apparatus for an internal combustion engine according to any one of claims 8 to 11, further comprising: Catalyst temperature detection estimating means for detecting or estimating the temperature of the catalyst disposed in the exhaust passage of the internal combustion engine;
Cooling time setting means for setting the cooling time based on the temperature of the catalyst;
The control apparatus for an internal combustion engine according to claim 12, further comprising: The EGR control means includes
And operating speed detecting means for detecting the operating speed before Symbol EGR adjustment mechanism,
An operation amount setting means for setting the operation amount of the EGR variable mechanism at the time of fuel cut based on the operation speed;
The control device for an internal combustion engine according to claim 1, comprising:   15. The internal combustion engine according to claim 14, wherein the intake air amount control means includes throttle amount setting means for setting a throttle amount of the intake air amount at the time of fuel cut to a smaller value as the operating amount is larger. Control device.   16. The control device for an internal combustion engine according to claim 14, wherein the operating speed detecting means detects an operating speed of the EGR variable mechanism in a region where the engine speed exceeds a determination value. The operating speed detecting means includes
An operating speed measuring means for measuring the operating speed of the EGR variable mechanism at an arbitrary engine speed;
A rotational speed storage means for storing the engine rotational speed at the time of measuring the operating speed;
Conversion means for converting the operating speed measured by the operating speed measuring means into an operating speed in a region exceeding the determination value based on the engine speed at the time of measurement;
The control apparatus for an internal combustion engine according to claim 16, further comprising: The EGR variable mechanism uses the hydraulic pressure of the internal combustion engine as a drive source,
The operating speed detecting means includes
An operating speed measuring means for measuring the operating speed of the EGR variable mechanism at an arbitrary oil temperature;
Oil temperature storage means for storing the oil temperature at the time of measuring the operating speed;
Oil temperature detecting means for detecting the oil temperature at a predetermined timing;
Conversion means for converting the operating speed measured by the operating speed measuring means into the operating speed at the predetermined timing based on the oil temperature at the time of measurement and the oil temperature at the predetermined timing;
The control device for an internal combustion engine according to any one of claims 14 to 17, further comprising:   13. The internal combustion engine control according to claim 12, wherein the cooling flow rate realizing unit and the flow rate changing unit control the intake air amount by controlling a throttle opening or an idle speed control (ISC) valve flow rate. apparatus. The intake air amount variable mechanism includes a throttle valve or an idle speed control (ISC) valve,
The internal combustion engine according to any one of claims 1 to 19, wherein the intake air amount control means controls the intake air amount by controlling a throttle opening or an idle speed control (ISC) valve flow rate. Control device.

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